Some DC fans are still trying to figure out just how much of the big twist from Joker was genuine and how much was made up by the aspiring supervillain, and one of the actors involved has since weighed in. As you might expect from a movie about one of the most mysterious characters from comic book history, Joker probably leaves viewers with just as many questions as it does answers for the Clown Prince of Crime's back story. One big revelation in particular has some viewers split over whether it's actually genuine or Of course, since we'll be talking about vital plot points from the movie, we must make it clear there are MAJOR SPOILERS ahead.

In Joker, Joaquin Phoenix portrays Arthur Fleck in a new origin story for the iconic Batman villain. The story introduces his mother Penny as someone Arthur cares for in their dingy apartment. Penny seems convinced local billionaire Thomas Wayne will provide them with the financial support they need if she can just get ahold of him, attempting to do so by way of writing letters. In a big twist, Arthur reads one of the letters and observes Penny telling Thomas he's Arhur's father. The revelation leads to Arthur believing himself to be a part of the Wayne family, visiting Wayne Manor and meeting a young Bruce and the family butler Alfred Pennyworth. A meeting with Thomas soon after results in the billionaire socking Arthur square in the nose.

Before punching him in the face, Thomas tells Arthur he is not in fact his son. Additionally, Thomas also reveals Arthur isn't Penny's biological son either, as he had actually been adopted at a young age. Arthur later looks at her medical records and spots his adoption certificate, seemingly confirming Mr. Wayne's version of events. It's implied that Penny had completely fabricated the story of Thomas Wayne being Arthur's father because she was insane to the point of being institutionalized at the time. However, a photo of Penny brandishing what appears to be a signature from Thomas Wayne shown towards the end of the movie is enough to have some fans again questioning which version of the story is actually real.

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With so much discussion about this plot point, Thomas Wayne actor Brett Cullen has even weighed in. Speaking with The Hollywood Reporter, Cullen says he approached director Todd Phillips about the relationship between Thomas and Penny, and the explanation he got made him feel like Penny may not be so delusional after all.

"The backstory was that Arthur's mother had worked for Thomas in his home, and she was a beautiful woman who Thomas was attracted to and it led to a physical relationship. Later in life, she's in and out of mental institutions. And in my mind, Thomas Wayne put her there."

This answer clearly shows the actor who actually played the part of Thomas Wayne believes Penny Fleck's version of Arthur's backstory. Cullen goes on to explain his character's point of view with this in mind, suggesting Thomas had Penny committed to presumably keep their affair a secret and protect the Wayne family.

"What I like about the film is that it's about real people with real faults who make mistakes. Some are done out of protection, like moving Arthur and his mother out of the picture.

Some viewers are going to feel more strongly about one explanation or the other about Joker's lineage. Still, given the events of the movie, it's impossible to be 100% sure exactly what the situation is. What isn't debatable is the end result, which has brought about the most dastardly criminal Gotham City has ever seen. Let's just hope this version of the Joker stays locked up in Arkham. Cullen's words come to us from THR.

Jeremy Dick