George Pal forgot to cast The Whipping Man and didn't realize his mistake until it was too late. Peter Sellers stepped in at the last minute and played the role, masked.
In addition to being an accomplished dancer, Russ Tamblyn also studied acrobatics and gymnastics. It is Tamblyn, not a stunt double, doing the many athletic moves.
Producer/director George Pal was good friends with animator Walter Lantz and would usually insert a Lantz reference in his films as an homage. In this film during the "Tom Thumb's Tune" sequence, when Tom is dancing past the rows of toys, you can hear Woody Woodpecker's laugh.
The head of MGM's British operations was so impressed that George Pal brought this film in under budget that he suggested that Pal submit a script for his favorite unproduced project. Pal chose The Time Machine
This marked the first time that producer George Pal directed a feature film. It was so successful that he directed his next four projects.
To help promote the film, a "Tom Thumb" float was made for the 1958 NY Macy's Thanksgiving Day Parade.