|Real name:||Martin Eisenberg|
|Portrayed by:||Clark Duke|
- "You guys never saw "One Night In Spider-Man"?"
- ―Marty [src]
Marty Eisenberg is Dave Lizewski's best friend who later becomes the superhero Battle-Guy. He is the tritagonist in Kick-Ass and Kick-Ass 2.
Marty is best friends with both Dave Lizewski and Todd Haynes, who he regularly hangs out with during school and at their local comic book store. When Dave questions Todd and Marty about why no one has ever took it upon themselves to become a real-life superhero, Marty remarks "Dude, if anybody did it in real life, they'd get their ass kicked. They'd be dead in, like, a day." which Todd agrees with, but Dave is unconvinced.
When Katie Deauxma pursues a friendship with Dave after he was "found naked and beaten in an alley" and believing that he is gay, Marty tries to convince Dave to tell Katie the truth, which he eventually does, and during this time, he becomes close to Katie's best friend Erika Cho, and attempts to "convert" her into a comic book reader by guiding her through various comics. Marty and Erika eventually become boyfriend and girlfriend.
Inspired by Kick-Ass, Marty decides to join the superhero team and creates his own costume. It didn't take long for him to join superhero team Justice Forever, under the alias of "Battle-Guy". although he is nervous thinking that he won't have a cool backstory like the others, so he makes up a lie saying that his parents were mugged and killed coming home from the opera, and the guy who killed them used their credit cards on porno sites, he is swiftly accepted into the team and becomes a member.
However, when Kick-Ass joined the team Marty started telling the others his story in his true story making Dave recognize him, Dave asks him why he made his story about his parents getting killed, so Marty is forced to tell the others that his story about his parents death was a lie, although he was trying to figure out how to tell the truth without sounding like an idiot, he said that he felt "out of place" as everyone else had a good story. and he was the only one without one, Even though he lied, he is quickly forgiven and let off the hook by the team's leader Colonel Stars and Stripes.
After finding each others' superhero persona, Kick-Ass and Battle-Guy regularly teamed up and patrolled the streets and rooftops, often talking about their mutual friend Todd. Eventually, the duo decide it's time they reveal their superhero identity's to Todd, asking him to join Justice Forever.
But they made fun of Todd's costume saying that since it was made out of tight Spandex, it gave him 'Male Camel Toe' and the name Ass-Kicker, but Marty called him Ass-Licker as a joke, but Todd fell out with Marty and Dave and joined the Toxic Mega Cunts.
Marty is with the team during their first bust, after Colonel Stars and Stripes located some mafia members holding prostitutes in their apartment. He was Night Bitch's savior during the raid, protecting her with his shield from what would of been a brutal knife hit.
But after the police hearing about the Colonels death and Night Bitch's assault, he is arrested by the police, along with other superheroes.
Then Dave's dad is killed by the Mother Fucker he attends the funeral, but is only out on parole, he survives the funeral attack by the Toxic Mega Cunts.
On the night that ended it all. Whilst playing a vital role during the battle, Marty joined the team in the fight between Justice Forever and the Toxic Mega Cunts, the weapon he uses is the 'Sic Stick' that Hit Girl used to get back at Brook and the other girls. During the battle, he knocked down a member of the Toxic Mega-Cunts before being knocked down by another member of the Toxic Mega-Cunts and drops the 'Sick Stick' accidentally activating it, he is about to be killed by the member. but is protected by Todd, formerly known as "Ass-Kicker" who uses the 'Sic Stick'. Not long after he swiftly made his way to the hanger rooftop, only to join Kick-Ass and the rest of the team.
- Battle Guy Suit: Marty wears a homemade suit consisting of a dark blue combat uniform with White Stars on the Shoulders and the Gloves, and Black Combat Boots. The suit also consists of a Blue tie-up mask with eye holes cut out and wears work glasses over them.
- Riot Shield: Marty has at least one Riot Shield to help protect him in battle, it is made of a plastic material with a blue and white star in the middle.
- Sic Stick: During the Battle of Justice Forever vs Toxic Mega Cunts, he is given Hit-Girl's Sic Stick.
- Dave Lizewski (Kick-Ass) - Best friend.
- Todd Haynes (Ass-Kicker) - Best friend.
- Erika Cho - Girlfriend.
- Katie Deauxma - Friend.
- Colonel Stars and Stripes - Friend and Mentor.
- Night Bitch - Friend.
- Remembering Tommy - Friends.
- Doctor Gravity - Friend.
- Chris D'Amico - Enemy.
- Canon (2 films)
- His other weapon is the Sic Stick, presumably given to him by Hit-Girl.
Differences from the comic
- Like his Comic Book counterpart, his costume bares a strong resemblance to Captain America except instead of the red, white and blue color scheme, it is blue with black vest with white stars on his mask, sleeves and gloves.
- His weapon is a plastic riot shield with a star printed onto it, in the comic he has two red metal riot shields with a silver circle around them, attached to the sleeves of his suit, while in the movie he only has one shield.
- Unlike his Comic Book counterpart, his mask is a tie-up and not fullface, and his mask has glasses.