This answer clearly shows the actor who actually played the part of Thomas Wayne believes Penny Fleck’s version of Arthur’s backstory.
In Joker, Joaquin Phoenix portrays Arthur Fleck in a new origin story for the iconic Batman villain.
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.
Additionally, Thomas also reveals Arthur isn’t Penny’s biological son either, as he had actually been adopted at a young age.