It's possible that you ended up hacking your game, that is really the only cause for Bad Eggs in recent Pokémon games. If a hack is possibly a bad or incorrect hack then you could get a Bad Egg.
By using a AR and catching someones Pokemon it will be called bad egg
If you are talking about the bad egg, it does not. That's why it is called a bad egg.
you get it from an egg in Pokemon platinum
You can not get a Turtwig egg in Pokemon Platinum. But if you breed a Turtwig with a Ditto, then it is possible.
There is absolutely no way to hatch it.
By using a AR and catching someones Pokemon it will be called bad egg
If you are talking about the bad egg, it does not. That's why it is called a bad egg.
It will corrupt your games' data.
The only ways to get a Turtwig is getting it as your starter or getting an egg from the daycare.
no you can't find a torchic egg in Pokemon platinum
Not sure if anyone has ever hatched a Bad Egg in Pokemon Platinum as they very rarely ever hatch. Although, in other games they have sometimes transformed into invisible, shiny, Bulbasaurs. Bad eggs have a record for messing up games. You shouldn't try to hack for it.
Use an Action Replay to import a Pokemon into your Party. Keep only the Bad Egg in your Party, and it should throw it away. If it doesn't work, you could be royally screwed, as it will eventually corrupt your data. If you ever receive a Bad Egg, don't save after getting it!
you get it from an egg in Pokemon platinum
You can not get a Turtwig egg in Pokemon Platinum. But if you breed a Turtwig with a Ditto, then it is possible.
it doesn't hach in to anything it just freezes your game
Don't hatch it unless you want your game deleted.
There is absolutely no way to hatch it.