I got a friend who did this. It's a funny story, actually, cause he does it with every game, but it gets particularly bad sometimes. He'll roll up to me and be all like, "Oh, I'm way past that part." Then in like a day he'll be like "I beat it already. Your still stuck at that part?" But when you go over his house you find walkthroughs printed out and guidebooks open on the game and stuff. So it's pretty funny.
So, this happened with Warcraft III. Our friend let him borrow it, and I was stuck on the stupid undead mission where you have to protect Kel'thuzad for a half hour. I'd had the game for a week, and I was a warcraft veteran, and he had it for TWO DAYS and told me he was already 3/4 done and near the end of the orc campaign. On the THIRD DAY, he told me he beat it. Now, I KNOW he must have cheated because he's never even played an RTS let alone a warcraft one. The closest thing was Starcraft and he cheated through that one too. About a year later, we're all gonna get together and play a lan for Warcraft 3, and he oddly doesn't want to play. While he's watching us play, he's seeing us do things like queue up buildings, set spells to autocast, healing our guys...and he's asking us how we're doing it all. He didn't recognize any of the units; when my Tauren Chieftain came out, he was like, "whoa! what is that guy?"
I looked at him awestruck. "You beat the game and you don't recognize him?"
His uber bull**** answer...
"No. I guess I must've never got that guy."
lol