Take a drink when Abby disappears, uses her wand as a phone, or turns something into a pumpkin.
Drink whenever Grover gives a dramatic faint on the ground whenever he either tires himself out or nothing goes right for him.
Drink whenever Ernie suggests a crazy game, two sips if Bert doesn't mind.
Take a sip whenever one of these characters is freaking out about something oddly specific: Ernie, Bert, Baby Bear or Telly.
Take a sip whenever Bert or Mr. Johnson falls backwards while moaning dramatically.
Drink whenever Don Music acts dramatic about not being able to write a song and/or points out a nonsensical lyric.
Take a drink when Baby Bear enthuses about porridge or art, Bert about pigeons, bottle caps or paperclips, Cookie Monster about cookies (two if he's talking about some other food), Zoe about ballet, any of the grouches about trash, or Telly about pogo sticks or triangles.
Drink whenever something mundane is treated as amazing (such as the "Lever Lover" song).