Overloaded melody?

It's common knowledge that the melody for both the alphabet song ("A-B-C-D.. E-F-G...") and Twinkle, Twinkle is the same. If this is coming as a surprise to you, try it yourself. It seems to me, though, that the melody is shared with at least one other childhood tune.

I put Olivia to bed the other night and turned on her Ocean Wonders Aquarium (which she absolutely loves, by the way). The song that started up was Twinkle, Twinkle. As I was leaving her room, I started singing to myself.

"Baa baa black sheep, have you any wool?"

I'm, like, "What the hell? That song is clearly 'Twinkle, Twinkle', so why am I singing 'Baa baa black sheep'?"

Now, I may totally be on crack here, but I'm pretty damned sure that the melody for all three songs is exactly the same. If this is true, I wonder how many other kids' songs also share this melody.

- Mike