If you're talking about that didi, then this article might help, but not as much as you would hope cause the answer is mainly: we're not sure why!
as far as i know, if u dint pee before going to bed, u will get a hard on next morning :D
I got this advise from doctor during circumcision
@ Draven: I do pee every night before go to bed but still in the morning .... :D
haha, maybe u drink a lot of water or beer, before going to bed :)
haha.. no Draven, I have been like this since I remember.. anyway, I think this question should be answered as "No Why" :)
Also, if you are executed, especially by a hanging, you can become erect and even ejaculate at the moment of death. It's called death erection or angel lust, and was observed with men who would sometimes ejaculate as they were hanged at the gallows. It's kind of a warm and fuzzy thought though that if I'm ever strung up and executed, my last action will be to cream my pants...