Cheating — in a pen-and-paper RPG? For real?

I ran across an offhanded reference recently to cheating in RPGs that stopped me dead in my tracks.

Cheating? In a pen-and-paper RPG? For realz? This is only, like, the complete antithesis of roleplaying itself.

I’m not talking about GMs fudging a few numbers here and there. That’s part of the social buy-in that we all sign up for at the outset of the game. No, I’m talking about a player changing the damage bonus on his sword, or neglecting to keep track of ammo in games where that matters, or “misremembering” his toughness save during the heat of the battle. Does this stuff happen?