!! OMG, he's naked: Mario Lopez !!
I openly admit that I preferred Zack to Slater back when I used to watch Saved By the Bell, but one thing both Mark-Paul Gosselaar and Mario Lopez have in common these days are amazingly nice asses. If you missed Mark-Paul's, I posted it back in June, but make sure you don't miss these stills from an upcoming episode of Nip/Tuck where Mario bares it all in a "homoerotic shower scene" with Julian McMahon [NSFW].
And just for fun, Mario and his penis jumping rope: