This discussion came up at a game last week. Under the newer Avengers Fantastic Four: Empyre Rule book, do you need to have the keyword to use TTPC? Can a generated Bystander, or a figure brought in from the side board use the TTPC if your starting force was a Theme?

Once your force is a themed team, it's a themed team for the entire game. As long as your starting force was determined to be a Themed Team during setup, you can have any friendly character use TTPC at any time (as long as they have not used Probability Control that turn), even if they did not begin as friendly, do not share the keyword, or did not contribute to the themed team (like a bystander).