That would suck. But it hasn't happened to me. I think I might have even gotten two game disks once...ehh, I don't think that's what happened. But I somehow ended up with two copies of Super Mario Galaxy 2. I'd still have two, but I tried to sell one at a garage sale, and the people running the garage sale(or someone, I don't even know) lost that and a bunch of other games I was planning to sell. Ugh.
Well, I got a game for Christmas that had the WRONG disk in it. xD; It was supposed to be Sonic Adventure DX, but instead Sonic Mega Collection was inside. At least it was still Sonic, though, hahaha! XD
sort of, one time I bought a brand new game with the wrong cartridge in it. it was a cheap ass budget DS game with like tennis and ultimate Frisbee on the cover but when I opened it up the actual game was a completely different monster truck/dirtbike racing game. didn't surprise me considering it cost like 5 freaking dollars, but I wonder exactly why it happened, did they just make a mistake in putting whichever games in whichever cases or did they run out of monster truck/dirtbike cases and decide to just put them in tennis/frisbee cases that were left over? as Ashens would say, "who knows and who cares?"