So for the record, about the record: the title is "Fly, Hippopotamus, Fly", by Ed Lipton, published by Gilead Music in (I think) 1970. It is a truly great album of kid's songs, and one of my major formative influences -- I can still hum a number of the tunes. There's the title song (If a hippopotamus can learn to fly, can a fly learn to hippopotami? If a fly can learn to hippopotami, then a hippopotamus can learn to fly!); "What Do the Animals Do?" (when it's five o'clock in the zoo); "The Spelling Song" (dedicated to the glorious irregularities of English pronunciation); "The Bubble" (about the grand adventures one can get into when you have just Too Much Bubble Gum); and many others.
I suspect that the album has been loved to death, especially since the paper insert was lost eons ago. But I shall have to see if it can be ripped to CD, and saved for posterity. (Especially since it's one of those items that I would actively recommend at parents.)