In an interview on Conan, Cryer describes how, when working on an episode of Two and a Half Men, they had to figure out how to show Kutcher naked:
We we’re working this over in the writer’s room, and then Ashton pipes in ‘oh, well I’ve got a huge prosthetic penis in my trailer’. We all had that awkward moment of ‘of course you do’.
You too can have one made. I had these web shorts that I did for my company and we were producing these various web shorts, like hidden camera things. One of the things that we did was this sketch called ‘Naked Man.’ We had this guy and we had him put on this prosthetic unit, and we sent him to interesting places… I was like, ‘Who knows when you’re gonna need a prosthetic penis?’ So, I kept it and I just happened to have it around.