"Hey, Big Zam!"
Big Zam, originally a type of mobile armored suit in the Gundam universe and a comparably overpowered playable character in Gundam: Battle Assault 2, is a meme from the Gundam: Battle Assault 2 episode of Game Grumps.
Without knowing anything about the characters, Danny picked Big Zam for his first fight with Arin and won easily. For the third fight on, except for the Ball versus Ball bonus round, Danny kept switching from a considerably less powerful character to Big Zam at the last moment.
Hey, Big Zam! and variants of that phrase are now used by Lovelies as stereotypical ADHD-esque phrases, which interrupt a sentence in the midd–hey, Big Zam!
(Gundam: Battle Assault 2, 3:39)
Arin: Maybe we should play as normal Gundams.
Danny: You're right, you're right.
Danny: I should mix it up.
Arin: laughing I'm gonna be, ehh, Big Zam again!
Danny: Yeah, no, I wouldn't do that.
Arin: I'm gonna be Psyco.
Danny: Hey, Big Zam!
Arin: Alright, I think I'm gonna have to go...
Danny: Oh, I like Sai.
Danny: Is that a girl?
Arin: I have no fucking clue, dude. ... I don't watch Gundam.
Danny: Y'h... Puru Two; are there two Purus?
Arin: Where's the original Gundam– there he is, Amuro.
Danny: Akahana looks pretty cool. Hey, Big Zam!
Arin: Alright, I think, uh, I think this round calls for... Big Zam. *laughs*
Danny: You son of a bitch, I can't believe you'd do that– Big Zam.
Arin: 3v3, baby!
Danny: Alright, yeah, wow, it– it all comes down to this. This is going to require a very special character, to which I cannot– I don't wanna divulge it right off– Big Zam.
Arin: We should have a Ball vers' Ball match.
Danny: Oh my god, I would, but I'm– I'm–
Arin: Can you back out?
Danny: I can't, I'm all wrapped up in this Big Zam thing. I'm in too deep.