They were first introduced on the USS Red Dwarf, but were not fully functional. Early models had optional extra groinal attachments, but later versions introduced to the USS Enterprise had them connected on as standard. Later models didn't walk like ducks, and could get the odd lady. Even if she was a Holodeck Character. At least, the services of a Holodeck jizzmopper isn't required, as Mandroid's are programmed to make sure the holocharacter swallows.