A Tiajuana Crime Scene is a combination of a Dirty Sanchez and a Hot Carl. It is very risky and few have ever pulled it off.
"I woke up this morning in the middle of a Tiajuana Crime Scene. If I had a dollar for everytime that happened..."
After partying continuously for a few hours, and still feeling fine, you sit on the toilet to use the bathroom, and it is then and there that you realize you are totally wasted.
"OMG you guys, I just had a bathroom realization, I need to drink water for awhile."
Basically, after you have butt sex and have poop on your wiener (Mudge), you wipe said poop on your partner's upper lip (Smudge). It's an updated term for a Dirty Sanchez.
Did you check out the Mudge Smudge that Bob left on Stanley? There was corn in it.