I do not get this... at. all. Even with your description.
Tom Hiddleson was not in Harry Potter. Tom Riddle was... but Tom Hiddleson did not play Tom Riddle... And The Riddle was played by Jim Carey... who was not Tom Riddle or in Harry Potter. Now Tom Hiddleson was in "War Horse" and so was David Thewlis. Now Thewlis was in Harry Potter... but he isn't the Riddler or Tom Riddle. I am trying here... But I still don't get this.
No really, I still don't get it.
However...
Tom Hiddleson was in "Midnight in Paris" with Adrian Brody who was in "King Kong" with Jack Black who was in "Tropic Thunder" with Robert Downey who was in "Gothica" with Penelope Cruz who was in "Vanilla Sky" with Tom Cruise who was in "A Few Good Men" with Kevin Bacon.
Adrian Brody actually has a Bacon number of 2... but I had to draw it out.