John Gamefreak decides that megas that aren't Zard and Mewtwo should get a 'X' and 'Y' version because he wants to shake every last shekel out of his consumers. He turns to (You) to create stats/concepts for them! What do you do? Try to make the mega have a separate niche to the other stone - not just an improvement. Try not to make them broken!

REMINDER: If its possible to draw a pattern from the only two variant Megas we have, 'Y' megas tend to be the more 'natural' progression from the base form.
>Zard Y just looks like base Zard but bigger/spikier and keeps higher SpAtk - Mewtwo Y is still a pure psychic Special Attacking nuke
>Zard X gains a dragon subtype, a complete change in colour scheme, and blue flames - Mewtwo X starts taking roids and becomes a physical attacker
Whether the mega we already have for the mon is the 'X' or the 'Y' is up to your discretion.

BONUS ROUND
Masuda calls in, and demands that you create a Mega Charizard and Mewtwo Z with +150 stats. When you ask him why, he replies
>Haha! I don't really know..
and hangs up.
What stats and design do you give them?