Toyman makes his bland debut as the newest Superman villain in Action Comics #64 (July 1943). In a world that already has The Joker and The Prankster, it seems like a pretty gimmicky idea, but whatever.
The only real memory of Toyman I have from my youth is from the phenomenal Alan Moore 2-issue story “Whatever happened to the Man of Tomorrow”, in which he and Prankster play a small role.