Finger in butt = ugh.
Penis in butt = ooh.
I think this has discouraged a tragic number of people from trying butt play. Because if something as small as a finger is so uncomfortable, anything bigger must be worse, right? Wrong. I'm not quite sure why, but it's completely wrong. A finger up your ass feels like a really unpleasant poop; a cock up your ass feels like a tight hard fuck. Strange but true.