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.
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.
The film's soundtrack was never released when the movie was back in 1967. However, two 7" 45 rpm singles including the main title song sung by Christy were the only original music releases associated with the movie.
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!".