Operation Kid Brother (1967), like many Italian films from the period, was filmed without any live sound and the voices were added later, in the studio. Neil Connery had appendicitis at this time and that was why he was dubbed in the film.
Quite a number of actors and regulars from the EON Productions James Bond series appear in this spoof even playing similar characters. These included Bernard Lee, Lois Maxwell, Daniela Bianchi, Anthony Dawson and Adolfo Celi.
When Sean Connery left the official James Bond series after appearing in You Only Live Twice (1967) which was released in the same year as this movie, producer Sabatello apparently offered the services of Neil Connery to Eon Productions who rejected the offer.
The taglines "'Neil Connery' is too much" and "OPERATION KID BROTHER is Too Much for One Mother!" are parodies of the tagline for the James Bond spoof movie Casino Royale (1967) which says "Casino Royale is too much for one James Bond!"
According to Lois Maxwell, she was paid more for this production than for all the Bond films combined.