I think it may be pretty dangerous if the big guy (the lead of gorillas) won't like you for some reason. Still very exciting!
I went to the Big Cat Rescue in FL years back, and back then they allowed you to socialize with the bobcat (you could pet it and (to the point) play with it). It was absolutely unforgettable experience. I was the only brave person to do it (but I love all kind of cats in general), and I still remember those poles as big as my own palm, and that cat dropping in front of me touching my toes so very gently (and the fur when I pet her was just so soft).