Zack Underwood
Gender: Male
Age: 14
Nemesis: Derek
King Pistachion
Professional Information
  The Lumberzacks (formerly)
Just Getting Started
Friends and Family
Eileen Underwood (mother)
Marcus Underwood (father)
Two unnamed brothers
Milo Murphy
Melissa Chase
Phineas Flynn
Ferb Fletcher
Love interests:
Jackie (previously)
Behind the Scenes
First Appearance:
  "Going the Extra Milo"
Voiced by:
Mekai Curtis (speaking voice)
Aaron Daniel Jacob (singing voice)
I'm trying to distract myself from the walls moving in on us.

— Zack Underwood

Zack Underwood is one of the main characters in Milo Murphy's Law, voiced by Mekai Curtis. He is best friends with Milo Murphy and Melissa Chase.


Zack is the new kid in town and the voice of reason when things get out of hand. While the rest of the town is used to Milo, Zack is trying to enjoy the adventure of being Milo's best friend without getting destroyed. He wants to follow Milo because he wants a change from common life. In fact, he accepts going to school with Milo because his adventures are unique ("Going the Extra Milo").

He also wants to be safe enough though. In the episode Sunny Side Up, he has no problems on doing a science project with Milo, even knowing that it's extremely hard, but when they made it he didn't let Milo get near to make the project safe.

It is possible that because he's new in Danville, he seems to not be fully aware of what Murphy's law can cause. He often says that things couldn't go worse, or he thinks that is some case, nothing wrong can happen. Zack is also fairly self-conscious about previously being part of The Lumberzacks, at times trying to conceal the fact from his friends while at others actually hoping to be recognized for the role.

Physical Appearance

Zack has dark brown eyes, brown skin, and thick, bushy black hair. He wears a deep-yellow short-sleeved shirt over a white long-sleeved shirt, revealing only the collar and the sleeves of the latter, alongside a pair of light colored blue jeans with pockets and gray cuffs. His sneakers are a darker blue and white with white laces.

He is slightly taller than both Milo and Melissa and tends to stand with a bit of a slouch, giving off a 'chill' appearance. Likewise, he often sports a cocky, relaxed expression to the same effect.


Click here to view the history of Zack Underwood.



Eileen Underwood

ChristmasPeril (521)

He was happy to visit his mom on career day and seemed satisfied when the other students noted how cool her job was. Eileen went with him when the school had a parent-teacher night, and the two of them exchanged friendly banter before the meeting.

Marcus Underwood

Zack expressed his worries to his father when they went on a fishing trip with Milo and Martin. While Marcus did not initially believe his son over the existence of Murphy's Law, the two of them ended up working together to get the boat to shore.

His father loves to scare him constantly- and would do so every Halloween, coming up with creative new ways to scare him every year. Zack absolutely loved this and claims it was awesome. His father manages to do it again recently despite Zack's belief that Halloween no longer scares him.


Milo Murphy

Main article: Zack and Milo's Relationship
Screenshot (3006)

Zack and Milo are best friends. While Zack didn't initially want to spend time around Milo over his condition, Milo's optimistic attitude won him over, and the two of them have been close friends ever since. Zack has a very cautious attitude and tends to worry a lot, but he doesn't mind the adventures they go on, and enjoys spending time with Milo. He often gives a voice of reason to Milo's carefree attitude, pointing out the worse parts of their plans and voicing his fear when tempting fate by doing things that might invite danger.

Melissa Chase

Main article: Zack and Melissa's Relationship

He became good friends with Melissa through their mutual friendship with Milo. Melissa often tries to get Zack to loosen up while Zack tends to worry about Melissa's absent-mindedness. As Milo's best friends, they share in the difficulties of dealing with Murphy's Law and often make bets with each other over whether events will play out the way they're supposed to.

The Lumberzacks

31 too much pressure

Before Zack moved to Danville, he and his former friends had formed a lumberjack-themed boy band. The five of them enjoyed their fame together until he ended up moving away, although the other members didn't seem too concerned about this. When he did see them again, the band's new leader, Max, provoked a rivalry between the now-renamed Lumbermaxes and Zack's new band, Just Getting Started. After the performance, they tried in vain to get Zack to rejoin.

Back when they were a band, they hung out together constantly, although they didn't seem to have the closest friendship. When a girl clearly cut in front of Max in a lineup, Zack went out of his way to claim that she wasn't in the wrong, starting a small argument with his bandmate over it. When he finally did leave the band, they barely looked up from their entertainment to say goodbye.

Max, as the voice of the group, doesn't seem to respect Zack much and tends to ignore his words in favor of hearing what he wants to hear, much to Zack's annoyance. He makes immature sounding assumptions that Zack is just using reverse psychology and secret messages to convey his actual thoughts.


Mort Schaeffer



Zack is on friendly terms with Mort. They are both players in the Jefferson County Middle School football team, and the two of them are a part of the band Just Getting Started. When Mort, like the others, was stressed out about their first live performance as a band, Zack reassured him it would be fine, managing to calm him down temporarily. And when Mort makes a bizarre comparison between Zack's past and a dance movie cliche, the latter excitedly agrees.

Amanda Lopez

Zack is on friendly terms with Amanda and has teased Milo over his interest in her. Like others, he finds her obsession with order unusual and recommended she switch to tangerine oranges to save time after finding out she had her entire day scheduled.

Chad Van Coff

Zack often seems amused by Chad's unusual antics, standing idly by while Melissa argues with him. When Chad made the suggestion that the punch was blood, Zack briefly pretended it was true to show how ridiculous that was. In spite of this, he was quick to go along with Chad's 'Vampire-hunter' theory and went out of his way to help him defend Mr. Drako.


Martin and Brigette Murphy

Screenshot (961)

Zack is on friendly terms with Milo's parents. When Brigette calls Melissa to ask her if they should invite Zack to the party, he informs her that he is fully insured, and even asks if they can make the party bigger. When he finds out that they'd accidentally donated Brigette's vintage T-shirt collection to charity, he works with Milo and Sara to get the shirts back as soon as possible. Zack is reasonably horrified when they return the shirts, only to find out that Brigette was planning on donating them anyway.

He tends to be a little nervous around Martin, knowing that the effects of Murphy's Law are multiplied when there is more than one Murphy in the area. He expressed this when he brings his own father on a fishing trip with Martin and Milo, and again when he voices his concerns about skiing with two Murphys. In spite of the extra danger, he enjoys hanging out with Milo's dad.

Sara Murphy

Screenshot (3524)

"Are you guys excited about the movie?"

Zack is on good terms with Milo's sister and enjoys hanging out with her. She spends quite a bit of time with the group, often ending up on adventures with them when things go out of hand. Sara, like Milo, was thrilled to catch him and Melissa up on Doctor Zone, although the latter two ended up more tired and confused about the show than excited. Afterward, while he seems to enjoy the show himself, he tends to find Sara's obsession with it odd.  

In We're Going to the Zoo, he hung out with Milo and Sara as they prepared some of Milo's clothing for donation. He claimed he didn't believe Sara when she repeated a conversation she'd had with her mother.  

Balthazar Cavendish and Vinnie Dakota

While Zack doesn't know them very well, he is on friendly terms with Cavendish and Dakota. Initially, he assumed, thanks to Chad, that the two of them were vampire hunters, and this led to his confronting them at a school dance. This impression didn't last long, and eventually, they were formally introduced to him by Milo as time travelers. Afterward, he helped them save the world from Pistachion invasion.


Zack is on good terms with Scott. While he's apprehensive of Scott's peculiarities, Zack is always happy to greet him. They'd originally met when Zack ended up underground with Milo and Melissa, and again after he'd been pursued underground with Melissa by Brick and Savannah. Scott helped him escape the agents and led him back up to the city.

Elliot Decker

Zack is often mildly annoyed with Elliot for causing them trouble, and treats his antics with skepticism, calling him out whenever he tries to exaggerate his job. In spite of this, he tends to be friendly with the crossing guard.


Zack had a brief crush on the danger-seeking girl, and he forced aside his typical cautious attitude to impress her. He was attracted to her for less than a day before he realized how dangerous she was.


Screenshot (2974)
The image gallery for Zack Underwood may be viewed here.


“You know, I don't know if it's the adrenaline talking, but I'm starting to feel like we can handle anything that comes our way.”
—Zack Underwood[source]

“If you never rest, how do you sleep?”
—Zack Underwood[source]

“Never get out of the boat. Absolutely right.”
—Zack Underwood[source]

We were regionally famous. The lumberjack thing was not my idea. My mom had a bunch of flannel and...”
—Zack Underwood[source]

“I’m too mesmerized by the thought of my own senseless demise!”
—Zack Underwood[source]

“If we don't sound great, these guys will really think I'm lost without them!”
—Zack Underwood[source]

“We're gonna grow old in here, and they'll find us when we're, like, twenty-four!”
—Zack Underwood[source]

“"The end"? What do you mean? She's about to fall into stampeding llamas. That's how we started!”
—Zack Underwood[source]

“So in order to destroy that big plant monster, we have to destroy the little one?”
—Zack Underwood[source]

“You're saying the man who invented the V-vee-neck sweater took credit for someone else's work?”
—Zack Underwood[source]

“Get out of the way, you stupid wolves!”
—Zack Underwood[source]

“So there's a parachute button but no engine?”
—Zack Underwood[source]


Season One

Season Two


  • In The Undergrounders, he appears to be claustrophobic, which is a fear of closed places; however, he says he's just 'claustro-avoidant'.
  • He states he has a fear of fish.
    • Though he has a least attempted to conquer his fear of fish that aren't in a body of water, he goes fishing in Time Out.
  • His football jersey number is 19.
  • Like Ferb, Zack has separate voice actors for speaking and singing.
  • Zack being the voice of reason yet a best friend to the main character who is positive is similar to Gerald Johanssen from Hey Arnold! Dan Povenmire worked on Hey Arnold! prior to working on Milo Murphy's Law.
  • In Fungus Among Us, he mentioned that he has at least two younger brothers who he claims can eat with their feet.
  • In Love Toboggan, it was shown he knows how to snowboard.

v - e - d Characters
Milo MurphyMelissa ChaseZack Underwood
Balthazar CavendishVinnie DakotaDiogeeMartin MurphyBrigette MurphySara MurphyAmanda LopezMort SchaefferBradley NicholsonElliot DeckerOrton MahlsonHeinz Doofenshmirtz
Richard ChaseEileen UnderwoodMarcus UnderwoodChad Van CoffElizabeth MilderKyle DrakoMs. MurawskiNolan MitchellScottMr. BlockLydiaJoni
Families Murphy: Martin MurphyBrigette MurphySara MurphyMilo MurphyDiogeeJoey MurphyLaura MurphyNate MurphyGrandpa MurphyGrandma MurphySheriff MurphyMurphy Family
Underwood: Marcus UnderwoodEileen UnderwoodZack Underwood
Chase: Richard ChaseMelissa Chase
Jefferson County
Middle School
Students: Amanda LopezMort SchaefferBradley NicholsonChad Van CoffLydiaJoni
Staff: Elizabeth MilderKyle DrakoMs. MurawskiNolan MitchellMs. WhiteFredMr. HartoonianMs. Whipley
Bureau of
Time Travel
Mr. BlockGretchenBalthazar CavendishVinnie DakotaBrickSavannah
The Doctor
Zone Files
Show and Cast: Orton MahlsonDoctor ZoneTime Ape
Fans: KrisWallyJosh
Phineas and Ferb
Dr. DoofenshmirtzPerry the PlatypusMajor MonogramCarl KarlPhineas FlynnFerb FletcherCandace FlynnJeremy JohnsonBuford Van StommBaljeet TjinderIsabella Garcia-Shapiro
Antagonists Pistachions: King PistachionDerekGiant PistachionDennisJerryBrandiPistachions (in general)
Other Antagonists: Sentient BlobVictor Verliezer
Kids and Teens: NealThe LumbermaxesMaxJackieBrulee twin sistersWendyLizzyLola SunderguardLola Sunderguard's Friends
Adults: Elliot DeckerScottVeronicaTobias TrollhammerClyde RickenbackerMr. BruleeMrs. BruleeMs. BaxterShelleyForemanDaveJavierSlashGretchen FlammkuchenPhillipGovernment AgentsJefferson G. CountyEuniceMayorCaptainSergio McGuinnessWilson
Misc: Lardee BoyC.I.D.D.AliensMinor Characters