How come my son is happiest when we change his diaper?

Hehe.. he's a nudist ;) seriously though, he probably just has a good association with diaper change time. As one of the other answerers suggested; how can we know what's going on in their heads lol. My little guy used to like change time too... then he started to go through the phase of squirming while getting changed (around 11 months) and now (13 months) he gets frustrated because he just wants down get get back to playing, so enjoy it while it lasts, no matter the reason for his happiness :D