I blame the lack of sleep that comes with being a parent to 2 under 3, but one time Addy requested to sing "Jesus Loves Me" and I accidentally started singing it to the tune of "Twinkle Twinkle Little Star" (aka, "ABCs" for those who didn't realize that that's the same tune). It totally fits, by the way, but it's REALLY hard to do it on purpose because you keep wanting to sing the words that go with the tune after you get through the first line or so. Let's face it, though, "Jesus loves me this I know, How I wonder what you are" just doesn't really make a lot of sense.
Along those lines, we're getting Addy used to coming into the church service with us on Sunday mornings. She loves to sing, but she doesn't read yet, so she and I just sing the words to "Jesus Loves Me" to the tune of whatever hymn everyone else is singing. It's gotta be interesting sitting near us at church.