Annie grew sick of being Annie for one night. She took on a different persona during Troy's birthday.
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Jeff and Troy spend time at a bar on the episode "Mixology Certifiction." It's the former's 21st birthday.
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Community Season 2 Episode 10 Quotes

Hello during a random dessert, the month and day of which coincide numerically with your expulsion from a uterus.

Troy [reading the cake]

Shirley: Here, let me help you with that.
Pierce: I broke my legs, not my gender.