I'm Superbad, your girl probably doodling my dick

from Big Sean – Supa Dupa Lemonade Lyrics on Rap Genius

This is a reference to the movie Superbad; in the movie Jonah Hill’s character used to draw dicks as a kid. Big Sean is using a play on words with the movie title, saying your girl draws his dick when she day dreams like Jonah Hill did in the movie.
http://www.youtube.com/watch?v=fzuvQXDUybE

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