Turns out I got Snuffleupagus's birthday wrong: first of all, it's actually on my calendar for today. Secondly, according to the Muppet Wiki, his birthday might actually be in January - in Episode 0331, Season 3, which aired on January 24, 1972, Mr. Snuffleupagus tells Big Bird that he is "two years old today".
And now I can't find where I originally got the idea that his birthday was today.
