I am not circumcised, and do not wish to be. When I was younger I didn't even know that penises didn't all have the foreskin, my father wasn't trimmed either.

The foreskin is a normal, natural part of the male sexual organs and is full of super-sensitive nerve endings. Unless your friend has phismosis or some other medical condition that necessitates circumcision I would advise him, highly, against doing it.

If his girlriend was with him because she cared about him she wouldn't ask him to part with such a pleasurable part of his anatomy. If he gets circumcised why not cut off her nipples and clitoral hood? It'd be about the same thing.