Only a genius can say this.
I am stupid.
Alright listen up, genius. The joke is that only a genius can say "EYE YAM STEW PEED" which sounds like "I am stupid". It's funny because it's unexpected that a genius would say they are stupid, especially after saying only a genius can say it. Also, Alana thinks that people who don't find the joke funny is a genius, which is the opposite of the truth.