At the time of this episode's broadcast Victoria Vetri was also Playboy's Playmate for September 1967 (as Angela Dorian).
The Royal Air Force don't have Colonels - Crittenden should have been a Group Captain
This is the first show where, in the opening credits, Richard Dawson/Newkirk is shown opening a safe. For the first 2 seasons, he was shown shuffling cards.
STALAG 2 and STALAG 16 are both mentioned. STALAG 16 is within driving distance of STALAG 13.
This is the only guest appearances of Naomi Stevens and Cliff Osmond in the series. They play two Underground agents aiding Hogan in his mission to blow up a tunnel.