The "Jackanory" scene from the second season finale.
"I promise not to twang his red braces... more than once."
Alex dirty dancing with Ray.
"It's not like I've SHAGGED AN ENTIRE RUGBY TEAM!"
"I bet she has."
Chris's reaction to the butt plug:
Chris: Must have bloody big ears.
Alex: Wrong orifice, Chris.
Chris: ... what?
Gene: It goes up your arse!
"They have sex, Gene. Sweaty, muscular, male sex. Get used to it."
In 1.07: While speculating on the perpetrators of an armed robbery Gene refers to the idea of a previously unknown gang as the New Kids On The Block, in 1981. Alex gives this a quick lampshade, drops it due to other stress, and is blindsided by Chris calling them the Back Street Boys from East 17 and Ray wants to get them Busted. Bonus points for Chris still somewhat being New Meat.
In 1.08: Alex, meet Pink Tank. Pink Tank, meet Unfortunate blue Ford Escort. Glorious.
"I'm imagining you imagining paying for sex with me in my imaginary role as an imaginary street whore."
Chris's striptease apology to Shaz from 2.01. Complete with Hot Chocolate's "You Sexy Thing" and dialogue. And his tripping on his undies while trying to kiss Shaz crowns it all.