Alfie: He's a complete psycho! He kidnapped Patricia!
Jerome: I think we would have noticed if Patricia'd been kidnapped. At the very least, it would have been quieter.
In the Season One finale, Jerome says he's "never going anywhere near Rufus again", only to promptly be texted by him. It's the little jump/uncomfortable shrug when he sees it that sells it.
Jerome: Speak of the devil. Literally. I'm surprised my phone didn't burst into flames.
Daphne's response to Victor's rant:
Victor: What we do know is that those nauseating, arrogant interfering children are somehow part of this!
Daphne: Do you sometimes think that you might be in the wrong job, Victor?
The way that Victor said "You! Boy! Bed! Now!" in House of Identity is quite laugh-inducing.
Victor kissing up to the guy who is considering whether or not to hold an exhibit on Ancient Egypt in Anubis House. Even the other characters find it hilarious.
Amber trying to teach Fabian to ignore Joy.
Nina's victory dance when she hears Fabian say that he's still in love with her.
Basically about half the stuff Alfie or Amber says qualifies.
Season three gives us Willow, who is just as good.
Willow: To [[Squee squee]] or not to squee...SQUEE!
From the Season 2 finale, when Victor discovers Mara and Mick talking in the hallway:
Victor: Mick Campell, Mara Jaffray, why are you not in your rooms?! (double take) Mick Campbell?!
And afterward, the way he shouted 'BED!' loudly and slowly, as well as the scared double takes the others make, is quite amusing. And after muttering to himself that he's let things slip, he quite loudly and hammily yells his usual words.
Season 3 premire: Fabian, upon realizing that KT is American, asks if she knows Nina. KT gives us a delightful response:
Dexter: He said it! That's like his catchphrase! (About Victor's pin drop speech)
Jerome: (Deadpan) Dude, we know.
How about the camera scene from season 1?
Victor reading Amber's diary. We get this little gem...
Victor: (reading) How can a man with such perfectly groomed facial hair be so horrid?
After which he promptly stops reading and checks his mustache in the mirror.
After Eddie's rousing speech during the dodgeball game, everyone is excited except for Jerome who is wearing a look of complete annoyance, due to being pegged hard with the dodgeballs before.
Fabian gives us two little gems in the same scene-
Eddie: I kissed Patricia...
Fabian: And now you're a zombie!
The second one happens when he's leaving the room. He passes by Patricia, and, due to hearing that Alfie and Eddie were both crushing on her, he backs away from her and says, "Get away from me," while she just looks at him.
Basically anytime the characters snark each other.
Mr. Sweet as a sinner, hamming it up the entire time. Telling a random student, "YOU LOOK LIKE AN ORANGUTAN," is just one of his many over the top lines.
The sinners in general. Sure, they're evil, but they have some of the best moments, and you can tell the actors were having a blast. Alfie was probably the funniest other than Mr. Sweet, especially when he started going through Jerome's phone to text everyone about a party (in order to turn them into sinners.) It's just his blunt lines that sell it.
Alfie: It must suck to be Jerome Clarke.
Speaking of sinners, their parody of Victor's catchphrase.