I checked it out from this guy talkign about it,it was the R/B/Y missingno sooo I wanted to no if theres any diff in R/S/E besides it being a question mark
Yes. There are actually two of them. The first one that looks like the Pokedex ? is very bad. You can only catch it by cheating. It is your default pokemon, so if you use the walk through walls code and don't get your starter, you can battle with it. But it has no moves, so when you try to look at them the game freezes. It can do all kinds of other harmful things to your game as well.
The second one, which looks like two big blocky ?s, is perfectly safe. You can catch it by sheer luck, so it is very rare, It's stats are about opposite of those of Shuckle, with very high Attack, Special Attack, and Speed. It only knows tackle, has no ability, and has a random nature like everything else. Ask MissingNo. Master if you want specifics, because he has one.