- Billina the Yellow Hen was actually named Bill by a farm boy who didn't know her gender, and the name stuck even after everyone realized she was a hen. Dorothy, who is apparently more traditional when it comes to names, changed her name to Billina. Incidentally, this means that both American chickens who came to live in Oz were named Bill at one point. (Ozma)
- I'm sure I don't need to say anything more about Cap'n Bill Weedles, the one-legged sailor who is Trot's constant companion.
- The circus in which Notta Bit More used to work had both a lion tamer named Bill and an elephant named Billy. I wonder if one of them was named after the other. (Cowardly Lion)
- An Un named Bill is the commander of the guard on the skyle, and his major Unish trait is being ungrateful. (Cowardly Lion again; Thompson obviously wasn't at the height of her creativity when writing this one.)
- Nickadoodle says that his telephone nose was invented by Uncle Billy, presumably a reference to William J. Hammer, an inventor friend of Thompson's family whom she called "Uncle Billy." (Cowardly Lion yet again)
- An even more direct reference to the real-life inventor can be found in Speedy's Uncle Billy, whose full name is William J. Harmstead. Speedy's real name is also William, although he rarely uses it. (Yellow Knight and Speedy)
- Billy Hastings is a member of Peter Brown's baseball team, and Peter fears he'll be made captain if he (Peter) doesn't come back from fairyland soon enough. (Pirates)
- Uncle Bill is the chairman of the club of uncles at Wise Acres. (Lucky Bucky; thanks to vilajunkie for reminding me of this one)
- Bill Bored (get it?), a lazy man who communicates with his pipe smoke, is the proprietor of Sign-Here. (Merry Go Round)
It's possible I'm forgetting some others, so please let me know if I am. Bilbil the goat doesn't count as Bill, does he?
Also, happy birthday to two people who aren't named Bill, burningofroissy and i3uffalogirl!