Charles Hawtrey was due to star in the show, and was featured in publicity in TV Times magazine, but fell out with the producers over billing.
A lot of the regulars were missing due to pantomime commitments around the country.
The "Elizabethan" madrigals were originally written for "Carry On Henry (1970)", but not used.
When Charles Hawtrey was offered a part, he demanded top billing but was only offered second billing or nothing and, refusing that, ended his time in the Carry On's.
This was the first Christmas special since 1970. There wasn't one in 1971, because that year's Carry On offering (Carry on at Your Convenience (1971)) didn't do very well at the box office.