This is the only "Carry On" film not to feature any actors who appeared in Carry on Sergeant (1958), the first film in the series.
Frankie Howerd was originally cast as the King of Spain, but died before filming started. The second choice was Bernard Bresslaw, who was busy appearing in the stage show Wot a Carry On in Blackpool.
Many of the younger cast members from "alternative comedy" backgrounds attempted to improvise their own material, but director Gerald Thomas angrily vetoed all their attempts, as he wanted this film to be true to the spirit of the prior Carry On entries. However, in the interests of fairness this also meant that Thomas had to forbid improvising by the few remaining Carry On veterans in the cast, something he later admitted worked to the film's detriment.
As critically panned as the film was, and as embarrassed as most of the cast were by the finished result, it somehow made more money at the UK box office than either of the dramatic Columbus films from 1992, 1492: Conquest of Paradise (1992) and Christopher Columbus: The Discovery (1992).