Tommy Thumb was a midget in Fritz Tiboldt's Circus in the 1940's. When the group was hired by the Nazi party to tour the United States and eliminate key military officials, he would be forced to do Tiboldt's bidding through threats and intimidation. Fritz would force Tommy to release a tiger from it's cage and set it to maul General Blaine of the US military. Spotted on the scene by Captain America and Bucky, they would fail to capture him. However, later Cap and Bucky would dismantle Fritz's operation.
Tommy's subsequent fate remains unrevealed, however as Fritz Tibolt would return to Germany and resume his circus, it is possible that Tommy resumed working for Tibolt. As such, it is noteworthy to mention that Tibolt would later be murdered by Nazi's who evaded capture in retribution of his failure, it is unknown if Tommy would have met the same fate.