I have to say, the best glitch I've ever had happen to me was in The Sims 2. To this day, I'm not sure why the game decided that its new goal in life was to snap my sanity into bite-sized chunks, but just thinking about it makes me crack up laughing.
I guess my little Sim was just That Tired, but he fell asleep with his face in his plate of spaghetti, like he could somehow just absorb it through osmosis. Okay, that's fine, right? I thought it was... until he somehow melted through the table, head-first. His head started rotating in a manner that would make the intro bug in Fallout: New Vegas proud and he sort of half-fell through the floor. He then proceeded to welcome his roommate home from his place Inside the floor, watch a little television while half-sunken beneath the couch and then he decided he needed a bath. I guess the floor wasn't clean enough for his liking.
By this time, I'm laughing so hard I'm in tears and the game decided to go for the kill. I've never seen a floor-bound Sim freak out like this, but he suddenly started flailing at the toilet like he was attempting to swim up to the ceiling, his arms stretched into alien shapes and somehow he managed to free himself from the floor just long enough to turn into a Dali-esque parody of humanity, babble to himself while thinking of the maid, and then fell asleep again on the bathroom floor.
The game crashed on me soon after that. I haven't played it since.