Blind Pew is named after a pirate in the classic adventure story Treasure Island.
Yellowbeard is obviously based on the infamous, murderous real-life pirate Edward "Blackbeard" Teach. Blackbeard wove hemp into his hair, and lit it to frighten his prey, as Yellowbeard does in the film. Also, Teach was known for murdering the target ships' crew in horrific ways if the ship resisted in any way.
The joke about Yellowbeard committing horrific acts of violence and thievery but being imprisoned for tax evasion is an obvious reference to 'Al Capone (I)'.
Marty Feldman died during filming of Yellowbeard (1983) on December 2, 1982 of a massive heart attack.
John Cleese has stated that he accepted a role in this film only as a favor to Graham Chapman, and that he thought the script was the worst that he had ever read.
Adam Ant was originally slated to be in the cast but had to bow out due to conflicts.