When Robert was a kid, he swallowed a small, shiny stone. It never bothered him, and he quickly forgot about it. Years and years later on the battle circuit, when under extreme mental duress, he mega evolves.

When he's like this, his inhibitions are loosened. No longer shy and polite, but aggressive and prideful(and also kind of a dick). Robert would help an elderly woman cross the street, but Robert X would race her to the other side and then rub victory in her face. It's a jarring difference from his normal self, to say the least.