1) It's a live-action episode starring Jon Benjamin as Master Shake, T-Pain as Frylock and Dave Long, an online contest winner, as Carl.
2) The episode almost didn't air at all and will run with a disclaimer. Why? ATHF co-creator is being vague with the details but has told The A.V. Club, "[Matt Maiellaro and I] were very close to posting the whole thing on YouTube… We did seriously consider it as the last ATHF ever (but of course we got picked up for more)."
Sounds like a good reason to tune in. Well, that and the chance to see T-Pain as Frylock of course.
