The Dogecoin Crypto-currency and Rifftrax seems like a match made in smartass heaven to me. Dogecoins users/miners love to spend Dogecoin and have in general have good sense of humor. They don't have a shady past like some crypto-currency, just lots of charity (http://doge4kids.org/) and goodwill (http://www.bloomberg.com/news/2014-02-04/jamaican-bobsledders-ride-dogecoin-into-olympics.html).
There is a huge Reddit community based around the coin and here is a thread on accepting Dogecoins,
How to Accept Dogecoin with your Business and Why (http://www.reddit.com/r/dogecoin/comments/1xfdsg/how_to_accept_dogecoin_with_your_business_and_why/)
Thanks for the suggestion!
We have just added it to the Donate Page http://www.rifftrax.com/donate
You can also test Dogecoin here: A7XhEHgxtDyvsqgr5YYZh71VkMHp8zLUBj