I was playing a GameBoy advanced game and I started fighting a Poke'mon named Missingno.. It looks a bit like a broken computer chip? Is my game defective?
Missingno should only look like that if you're playing the old Red, Blue or Yellow games, I believe. It's in every one of those game, and it's really just a bug. The old games had a lot more bugs and glitches than the new ones do.
If it is R/B/Y you're talking about, there is a stickied thread in that section to talk about Missingno: