Hot off the heels of Day of the Devs, a video was posted on Double Fine's YouTube account today announcing -- and showing proof! -- that Pendleton Ward (best known as the creator of Adventure Time) will be lending his voice to Broken Age. The video's description says that he'll play the part of "the lovable Gus," so it's not clear if this will be a character present through the entire game or a one-off scenario where you encounter him.
At any rate, we at least know that Gus will be stuck in a tree, hooked by a branch on none other than his underwear, and it'll be the voice of Pendleton Ward behind the character screaming at you to unhook his underwear. So, basically what anyone would have expected a character voiced by Pendleton to be like.