Bruce Banner Penis Syndrome (otherwise known as BBPS or being a 'grower not a shower) is what happens when your penis is soft it is small and when hard it is large.
Much as how when Bruce Banner is calm he is small and puny Banner, and when he is angry he is huge and angry Hulk.
Girl: Hey are you a grower or a shower?
Guy: I actually have Bruce Banner Penis Syndrome
Girl: ...so a grower?