It was a creative decision that damn near sank the Indiana Jones franchise. When Harrison Ford returned to his iconic role for Indiana Jones and the Kingdom of the Crystal Skull, he was given a son. And that son was played by Shia LaBeouf. Now, maybe Mutt Williams was a non-starter no matter WHO played him. But the good news is, the lesson seems to have been learned, as Muttwill NOT be back for the in-development Indiana Jones 5. Current screenwriter David Koepp, who also penned Crystal Skull, updated the status of the sequel and said:
"Harrison plays Indiana Jones, that I can certainly say. And the Shia LaBeouf character is not in the film."
Well, that gives us a lot to unpack. If you step back, you can see the final moments of Indiana Jones and the Kingdom of the Crystal Skull as a sort of baton-pass from Indy to Mutt, with the famed archeologist's hat blowing down a church aisle, and the son picking it up and almost putting it on. Indy grabs it back, with a "Not yet, kid" nod, and we all laugh... because no one wants to come watch the Mutt Williams Adventures on screen.