Henry II in A Man for All Seasons and A Lion in Winter
Close but not quite. Those are two different Henrys: The one in A Man for All Seasons is Henry VIII (played by Robert Shaw), while A Lion in Winter is Henry II.
Interestingly, the other O'Toole-as-Henry II movie also has him killing a trusted friend / former advisor.
Peter Gallagher and Marlon Brando?
What's his name from Guys and Dolls. Masterson?
I got my Thomases confused! A Man for All Seasons is Thomas More, and the other Henry II movie is with Thomas A Beckett and I can't remember the name of it offhand.
Kevin Costner and Henry Fonda
Laurence Olivier and Ian McKellen.
Costner and Fonda's gotta be Wyatt Earp?