It’s weird what you can turn up when you do just a brief Internet search for a commonly known topic. In this case, it’s that Mr. Snuffleupagus’ parents were going to get a divorce, but the episode didn’t test well with children, so they canned the episode. Strange, no? Snuffy is an interesting character anyway, starting life as Big Bird’s imaginary friend, but gradually becoming a real character. Throughout a lot of the run of Sesame Street, and certainly from the show as I remember it in my own youth, Big Bird’s adult friends would constantly miss Snuffy, either because of his leaving at the wrong time or simply because something was blocking their view of him. There were occasional hints that he did actually exist, including his occasionally sending oversized postcards to Big Bird when he was out of town. I understand that in 1985, they decided to have the adults actually meet Snuffy, both because they were running out of ways to have people just miss him and because of the more serious reason that they thought nobody believing Big Bird would discourage viewers from telling their parents about real problems. He’s also apparently less constantly depressed now than what I remember, possibly because his very existence isn’t constantly in doubt.
Snuffy is basically a woolly mammoth, although he lacks tusks and has a much larger, thicker tail. His first name is Aloysius, he’s four years old, and he has a younger sister named Alice. Other Snuffleupaguses (Snuffleupagi? Okay, probably not) have shown up from time to time as well, and I think it was even established that he has relatives in Hawaii, despite the thick fur not being particularly suited to the climate there. Oh, and his favorite foods are cabbage and spaghetti. It takes two people to perform Snuffy, with the one in the front providing the voice.