A full bladder is no joke.

Extras on the set of the upcoming “Joker” movie were locked in a city subway car for more than three hours during weekend filming in a Brooklyn train station — and were forced to relieve themselves on the tracks, TMZ reported.

The extras were filming a scene in an unnamed subway station and denied their break after two hours of work, sources told the outlet.

Things apparently got so bad that the desperate actors banged on the subway doors, pleading to be let out — to no avail.

They eventually did their business on the tracks in between the cars, according to TMZ.

A complaint was lodged with the Screen Actors Guild, which will continue to monitor the situation, the outlet reported.

Warner Bros. is also investigating the incident, TMZ reported.

Joaquin Phoenix, who will play the DC Comics villain, was spotted filming in full costume Sunday in a Brooklyn train station.

“The Joker” is set to be released in the US on Oct. 4, 2019.