Chang being called "Teacher Chang," and not professor.
Shirley's "the Lord is testing me" and Jeff being the lazy atheist.
When Annie said about Vaughn showing her a pumpkin-shaped cloud (normally hated that scene, ehhh), Abed was the only one who looked at the sky searching for it.
Don Draper (Abed) hitting on Trudy! "Abed! What are you doing?" "Don Draper from Mad Men. What did you think?" "Weird!" "Awesome!" "Put your tongue in her ear!" "I liked it!" "Don't be like him, he cheats on his wife. Be someone nice like Mike Brady. "
Abed doing a Jeff Winger, too.
Jeff singing Chainless Melody to annoy his pottery instructor (who happens to be Buster Bluth!).
Annie's "vase."
Leonard's pranks to Dean Pelton.
Senor Chang being afraid of frogs.
Annie running after Jeff with a pepper spray when she was playing campus cop with Shirley.
Annie banging Jeff's head on the table.
AnniesBoobs!
Funny Troy/Abed doing elevator, stairs and escalator gag.
Annie & Jeff "the Annie of it all" moment, him doing her a Heimlich in dreamy slow-mo.