that when I fly...

My dick is so big; that when I fly, it has to take the train.

http://www.101funjokes.com/big_dick_jokes.htm

clowns climb out of ...

My penis is so big, clowns climb out of it when I cum.

http://www.jokes-db.com/jokes/big-penis-jokes

has better credit than ...

My penis has better credit than I do.

http://www.jokes-db.com/jokes/big-penis-jokes

has an elevator and a lobby...

My penis has an elevator and a lobby.

http://www.jokes-db.com/jokes/big-penis-jokes

it graduated a year ahead ...

My penis is so big, it graduated a year ahead of me from high school.