This whole bit is made all the funnier by knowing that all of the guards were just random extras who weren’t told what was going to happen only that they weren’t allowed laugh at any cost as they wouldn’t be payed if they did.
No it isn’t, because that’s not true. People on Tumblr seem to have a very, very odd idea of how films, especially comedy films, are made. A scene like the “biggus dickus” one relies on some very precise timing, and could not possibly be made in that way. Even if it could, all the actual extras in Life of Brian were Tunisians who didn’t speak English, so they would have had no difficulty whatsoever in not laughing.
The actor shown in the photos above with Michael Palin is Chris Langham, who was one of the most famous people in British comedy until his 2005 arrest on child porn charges, and was very well known as a stand-up comedian, actor, and TV star — he was also the real-life husband of the actor who played Judith in the film.
The other giggling guard is Charles McKeown, who is better known as a writer (he co-wrote several of Terry Gilliam’s films, among others), but also had acting roles in many comedy TV shows, including Hitch-Hiker’s Guide To The Galaxy, Fawlty Towers, Ripping Yarns, and Yes Minister, and small roles in quite a lot of dramas and films.
Both men play other roles in the film, too — Langham is one of the people being crucified in the “line at the door, one cross each” scene, while McKeown also plays one of the prophets and the blind man who claims to be healed in the juniper bush scene.
It’s not a funny scene because someone played a cruel trick on low-paid workers, in other words, but because professionals who were very good at their jobs put in the work…