No, OverUnderAround, the only thing that is different, is that the green part on the front of the case feels a bit fuzzy. That's all. I think it originally depended on where you bought your set.
Yeah, DS, everyone's right. It's a laugh-track. However, as the series progresses, the quality of the laugh-track increses. I find that the laughing feels much more natural in the later-season episodes than it does in the first. But it's still pretty good.
Also, interesting tidbit: The Steve Martin episode (I believe it's season two, someone correct me if I'm wrong) has no laugh-track. In this episode, Kermit has cancelled the show and scheduled auditions for new acts. Steve Martin was scheduled to be on the show that night and is a bit disgruntled that he isn't, and he 'auditions' with a few of his acts, like the Balloon Animals, and two acts where he plays the banjo. Also, everyone is nervous that they will be replaced, so everyone tried to stop acts that would be their 'replacements' from finishing their acts. It's great fun. But the laughter is actually the laughter of the cast and crew. Since there is no audience in the episode, there is no laugh track! Cool, eh?