What exactly is a bad egg in Pokemon?

So my friend got a cheat machine and he said he caught a trainers pokemon but when the option said "would u like to give *pokemon's name* and nickname. However it said bad egg instead of the pokemon's name he also caught one that had a blank instead...

So I have a question about Bad Eggs in pokemon. I have pokemon diamond and pokemon black. I used an action replay wild modifier code on pokemon diamond and basically leveled them up with rare candies. I transfered some of the pokemon to my pokemon black...

Okay. I was using action replay to try to get a Ditto egg, And it gave my a Bad EGG. i was reading about bad eggs and how to hatch them, And i found out about MissingNo. But, i also read that Bad EGG's status will say "This might take a Long time...

Hi there. (: I used Pokestation Database to hack a few event pokemon or something, and I'm not sure what they are, but I now have six eggs, all with the same thing: A quite mysterious Pokemon Eggs that was obtained in ________________. "The Egg...

i used a cheat to get a super lucario and i got a bad egg i saved it when i didnt know that a bad egg cant hatch now i cant use six pokemon in my party because it wont let me release it or store it in my pc when i try to store it it says detach ball...

I know you get Bad Egg through cheating. But if you get a cheat/glitched up Pokemon through trade or GTS, will it affect your game to get Bad Egg or just the person who cheated?

My stup** little bro got an bad egg in pokemon pearl and noe hes crying cuz he cant remove it. Whats the action replay code to remove a bad egg?

ok in my pokemon pearl i put in a code called instant egg and i got it from the daycare center place and now it hatched and it has a question mark and i can't put it in my mail box thingy in the computer and when i go to "pokemon" when i press...

I desperately need to own the 'trophy' in pokemon emerald that is the shiny pokemon, but when i use the gameshark code I ended up having a bad egg. when I keep it in my pc it multiplies. Help a poor desperate guy like me please.