Well done Ryan, I'm surprised a few other people didn't remember, it was mentioned in the Tibby's Bowl / Muppet Central interview with Louise Gold a few years ago (she was asked for her most embarrassing moment on TMS).Ryan said:No, they knew it. But it was the last thing filmed that day, so they had no time to reshoot it. That Whatnot is being played by Louise Gold.
Actually, if you watch that skit carefully, its noticeable that that Whatnot is ducking in and out of the scene a lot, which has the unfortunate side effect of drawing rather more attention to the puppet having only one eye, than if it had been moving a bit more normally it wouldn't have been so noticeable. I've sometimes wondered whether Ms Gold (who was a rather inexperienced puppeteer at the time) might have been trying to (unsuccesfully) hide the fact that the puppet wasn't quite as it should be...