I've had the micro penis that after he came his penis actually went introverted. Felt so sad for him, he was so pleased that he had managed to cum ... At least I'd made him happy that way.
I've had one like that as well, he was really overweight and because of that his penis had kinda gone into itself, I had to stick my finger in it to reach his knob end..
He did manage to come that way amazingly enough!!
Any other very small penises I come across usually only want oral because they know they won't be able to have sex.
I feel sad for the ones who are really bothered by it, but a surprising amount of clients with very small ones seem to be ok with it, unless that's just an act..