There is no animation studio or artist credited on the Muppet Wiki article for the Hero Guy series, so I can only assume it was the work of one of the in-house graphic designers. Probably Pete Oritz. I wanted to say it was Joey Ahlbum, who also around that time was combining his animation with live Muppet segments, and it could be, but it probably isn't. Of course there is also the possibility it was done by David Rudman's studio Spiffy Pictures. Anyone else care to take a guess?
On a different note, I love his character design! He looks like he could have been a cereal mascot in the 60s or 70s. Reminds me a bit of Quisp, specifically.