Originally Posted by Shadow Tyranitar
What? What? If I trade the egg of a Blastoise to emerald, it'll be a bad egg?
Trading Pokemon will not give you a Bad Egg, only cheating to get them.
If you're playing FRLG, you will only be able to trade with Emerald after you've gotten the National Dex on Emerald anyway.
If you're playing RS, you will not be able to trade non-Hoenn Pokemon (including eggs) to Emerald until you have the National Dex on Emerald.
So you can't get a Bad Egg from that anyway seeing you can't trade.