A TV show "Friends" co-stars share a moment.

A continuity error in Friends has left some fans feeling rather confused.

With lockdown dragging on in the UK, many people are passing the time by re-watching the beloved sitcom’s 10 seasons.

One such person was TikTok user bronniiiieee, who noticed that the father of Ross and Monica, usually played by Elliott Gould, took on a completely different appearance in one episode.

The instance occurs in the eighth season’s 18th instalment, which is titled “The One in Massapequa”. It sees the main characters attend Ross and Monica’s parents’ 35th wedding anniversary party.

At one stage, when Ross turns to his dad, Gould is nowhere to be seen.

In his place is an unidentified actor who looks nothing like Gould, prompting the TikTok user to ask: “In all my Friends fans years, how have I never noticed this guy before?”

Cast members of the comedy series 'Friends.' TNS.

Digital Spy cleared up the blunder, though, when a fan pointed out a similar occurrence in the past.

These "errors" are due to how the series is now shown compared to how it was filmed.

Back when Friends was first airing on TV, it was shown in a 4:3 aspect ratio.

However, it's the wider version of the show that has now become standard, which means that viewers are able to see the stand-ins and extras they would have never seen before.

This man was merely standing in for Gould and was always intended to remain off-camera. Case closed.