For thos in need of a little background:
A little while ago Powerhoof's Barney Cumming posted a gif of the Valve Corporation co-founder dragonpunching a hapless fighter in Crawl - the studio's local multiplayer dungeon crawler.
The gif ended up getting a lot of traction online and a nervous Cumming decided the best thing to do was to send Valve an email asking permission to keep Newell's likeness in the game.
Here's an excerpt from the explanatory email - Cumming's main strategy is to sell the concept as a self-defence measure (the bearded incarnation is apparently Newell's Super Saiyan form):
You will be the most powerful character in the game, effectively building a perception in Crawl players that you would be a formidable opponent in combat. This would surely reduce the desire to battle you among our players, barring edge cases in which the player is incredibly powerful himself and is looking for a worthy opponent.
Cumming now posts that Valve replied with a "short sweet email" giving the go-ahead for the character.