Some of my favourite moments/themes:
1) the chicken impersonations. Started with Gob but in later episodes each character then began doing one, then they all did them simultaneously. Each radically different and hilarious.
2) Stan Sitwell and his alopecia. Especially the gag about him not being able to buy another convertible car (wig loss factor) and Gob going with Stan's wigmaker to get his dress eyebrows. Gob is later seen with odd looking eyebrows. "Are those Stan Sitwell's?" asks Michael. "They just make me feel... dressier..."
3) "Pop-pop" in the attic. "The fact that you call it that shows you're not ready..."
4) Barry Zuckercorn's total and utter incompetence as a lawyer, and his barely disguised homosexuality
5) The doctor whose announcements are horribly literal. "We've lost him..." - cue distress at the death of George. When in fact George has gone missing.
6) Franklin, the foul-mouthed puppet. Genius.
7) Kitty lifting her top to show her new fake tits. "Say goodbye to these...".
8.) the sad walk all the characters do when they've been dumped...
9) Tobias' cut-offs and the whole 'never-nude' stuff. And his even more obvious homosexuality.
10) Anne. "Her?"
11) Le Cousins Dangereux and the whole inter-cousin longing.
12) Buster and the loose seal - another "Lucille" ruining his life.
13) the police aggression to Oscar, with one policeman always weighing in with a truncheon just as Oscar's been fully restrained.
14) "Girls With Low Self-Esteem" - the best DVD series ever.
15) the Cornballer. Especially the version in Mexico.
16) Tobias' desperate longing to be in the Blue Man group. "I just blue myself" Cue Michael: "You really oughta record what you're saying..."
17) Michael Bluth giving his son a mixture of his name and his father's name. Welcome, George Michael...
18) The boat Gob buys - The Seaword. "We need to get rid of the Seaword." says Michael to Gob. Lucille, overhearing, thinks he's referring to her...
19) Lucille 2's (Liza Minelli) vertigo. Classic visual gags.
20) Uncle Jack's (Martin Short) "Swoop me!" thing. And when Dragan, his helper, shakes him till he vomits. Also this... Jack: "To the nuts! ...The bridge mix! The bridge mix! Fool!"