You know, I have a possible theory. Dunno if you remember or know about these, but there were these two-piece jigsaw puzzles with Sesame Muppets to teach counting from 1 to 20. The character with the number was one piece, and a matching number of items for each Muppet along with the word form of the number was on the other. Yes, Prairie was included in the set, 17 with seventeen jacks. But there was this lavender female Anything Muppet cheerleader with the 4 on her jersey, and four footballs. What I think is they maybe confused the characters? Especially since it was back in the early days of Sesame? Other than that, I'd write up the question of why Prairie sang about wanting 3 footballs for Christmas and send it to Steve at the MuppetCast to see if he'd forward it to Fran Brill in hopes of getting an answer.
Hope this helps. *Disappears.