I thought that was Dave Goelz as Robin; he has a bit of Chip in him. All I can think of is this:
So they hammer in the point in the early episodes that Piggy didn't remember Gonzo or Fozzie or any of the core characters besides Kermit, but she remembers Robin, who I remember her having barely, if any interaction with.
I think the whole "Who are you?" bit would have been funnier here with Robin; a cool character who has been ignored and very inconsistent with his appearances lately for no apparent reason. Maybe the reason they kept him out of the limelight for so long was because they didn't have a proper voice actor, which sadly is still the case, but I don't mind or can fault them for trying.