From the Shirtpunch.com's interview with the artist:
"Question: What inspired this design?
Answer: It goes with another similar design, which also mashes rather well... PokÉwok and Pikachewie (http://bit.ly/vm0dX7). I suppose it started with Pikachu/Chewbacca, but Pokéwok was always planned."
About Shirtpunch.com: It's simple; ShirtPunch is your home for limited edition, pop culture tees... but there's a twist! We only offer one shirt every 24-hours, and they're always only $10.