Obscurity factor: 8
This 1963 one-off cartoon from Warner Brothers has the Chuck Jones stamp all over it. George and his wife Prunhilda want a child in the worst way. Prunhilda knits booties until the home is inundated with them. One day, a passing wizard - Ralph K. Merlin Jr. - overhears their plight and answers Prunhilda's wish for a child, even one only as large as her thumb. The happy, if nonplussed couple is presented with Tom. Through a series of remarkable circumstances he becomes a knight in King Arthur's court.
Like many one-offs, this short can be found on Warner Brothers compliation DVDs, but it can be hard to pinpoint which ones. The full short above was uploaded by dimitarlull to VBox7.com - a Bulgarian YouTube. It takes a while to load, so while you're waiting, have a look at the clip below, which was cut from the broadcast version, presumably because they didn't want irate parents calling the network and yelling at them about their children running around saying "ass".
The clip above was uploaded to YouTube by Itclassics.
Obscurity factor: 8 (occasionally screened, hard to find, marginally remembered)