Worst mistake to ever make in the Pokémon world...

[kr9q]

Try to beat up Primal Dialga!
Jump off a cliff!
Play Curby on Primal Dialga while he is flying!

[Nightmare Eater]

Steal a Yamask's golden mask.
Hug Lucario.
Use Body Slam on Ferrothorn(Unless you can break steel!)

[kr9q]

Buy a flat screen tv and try to hook it up to a Bonsly.

[ShiraBliss]

^ ... what?

Be fooled by Cofagricus' disguise and have your soul and body eaten by it when you get too close.
Eat baby Cherubi right in front of mama Cherrim...
... especially when it's sunny out.

[kr9q]

^I thinks its funny
Follow a litwick.

[Sceptile987]

1)Saying that this place sucks and that yu-gi-oh cards are waaay better than pokemon cards, that would really pee 'em off, so dont do that
2)Bringing the Animal Liberation Front in to the pokemon world
3)bringing Chuck norris into the pokemon world
4)Crossing the streams
5)Bringing LittleBIGPlanet into the pokemon world, the pokemon would stand no chance!

[kr9q]

Try to use a chainsaw on a Sudowodo
Try to fly
Try to hock up a flat screen to a Geodude

[Jake & Infernape]

Try to hock up a flat screen to a rock

How is that pokemon related?

[spritey]

Tongue to tongue with Lickilicky. D=

[Aggron is awesome]

- Challenging Uxie to a staring contest

[Julez]

Going out in the wild without pokemon! seriously it wat all people tell you

[Latias Tamer]

I'd say setting up an evil pokemon gang bent of taking over the world...just as a 10 year old sets out on his journey. Pretty fatal mistake there. =p

[Reshurott Inferno]

Not remembering to incapacitate the local PKMN Prof., so the 10-year-old can't start his journey.

[Mondo Oowada]

Using a male Gardevoir.

[ShiraBliss]

Mistake a male Kadabra for a female.

Yoroshii's Sandslash made that mistake...