I don't think I could.. I would know how to fake the noises and the "look", think I could do an ok job of that (varies by person anyway, depends how well they know you) but I'd just feel reallllly silly pretending... If they figured it out (not that hard really with us blokes - the evidence or lack of really is just too obvious, and if you're in contact with his scrotum/perineum area you can tell too) what are you going to say? I'd be so embarassed.