The music played during the first and last scene involving Matt Helm was Dean Martin's 1964 hit Everybody loves Somebody Sometimes. It was Dean Martin's only song that topped the Billboard Hot 100 during the 60's.
To create the effect of Sheila's half orange, half purple dress and skirt being unzipped by the villain's gadget, thin wires were attached to the zippers on actress Janice Rule's clothes and then pulled on by off camera crewmen, effectively stripping the actress while leaving her clad only in a strapless slip.
When Matt is standing in front of the wall as the firing squad is getting ready to execute him, he asks for one last cigarette. The guard next to him offers him one and as he takes it he says "I'll remember you from the great beyond, somewhere around Steubenville, I hope." This is a reference to Steubenville Ohio along the Ohio/West Virginia border, the small town where Dean Martin was born in 1917.
Janice Rule later said that she regretted appearing in this film, saying that it was the worst movie she was ever in.