The puppet that started out as Warren the Warthog appears in the film, but we can't get a screenshot yet. The warthog (played by Bill Barretta) is in the same scene as a crab played by Brian Henson as seen in the film's B-roll footage.
I've definitely seen the crab in HA stuff, but I'm trying to figure out if it originated as a Muppet. We have Cornelius the Crab and I see that the HA Wiki documents at least three differently colored crabs. The one in Happytime looks more like the green one based on the chin, but maybe recolored. The horn-rims on each of them seem to have specific patterns, too.
Anyone with a keener eye than me spot anything conclusive?