"We've been burgled- someone's nicked me Grandma!" (After Carl and Marty's Zany Scheme involving burgling some burglars went wrong. They stole an urn, under the impression that it was a football trophy)
Mimi Maguire forcing her way upstairs in series 3, with the Gallaghers trying to hold her back by throwing furniture at her. One of them resorted to Looney Tunes tactics and stuck a child's rubber ring over her head.
Every other scene with Kev and Veronica.
Every other scene with Micky Maguire.
In the American series:
After half an episode of suspense as to where Frank has mysteriously disappeared to (including a scare where they thought a dead homeless guy under the El train was Frank), it's finally revealed where Frank ended up: Toronto!, complete with Frank looking bewildered at the CN Tower and the Canadian flag
Frank's subsequent arguing with the Canadian jail guard is also hilarious
The photos of the Gallaghers with their adopted families the last time their family was broken up by social services, including a totally random shot of Liam having been apparently adopted by disgraced politician Rod Blagojevich
Frank blinding his eye with a Luger pistol after loading it with the wrong bullet.
Lucy Jo chasing Fiona down the street with a baseball bat in one hand and her baby in the other.
Fiona later telling her to just beat her with the damn bat.
From "A Bottle of Jean Nate", Kevin getting high on cocaine and Jody's crying after sex and listening to Kiss From A Rose by Seal during sex.
Estefania kicking Lip in the back of the head while having wild sex with Marco in the back seat of Steve's car, who is her husband, until Lip just straight up leaves.
The glorious Mood Whiplash of seeing a bare-ass naked Marco pinning Steve to the floor with his foot, with a corkscrew in his ass, right after Lip gives an emotional goodbye video message to his child.
Carl kills a bald eagle so the family decides to have it for Thanksgiving and save the turkey for later. After finding out how illegal what they doign is, they quickly dispose of the tracker the bird has attached to its leg.