Karate Kid Macchio had his own trilogy in the works when "Back to the Future" was offered, but little did he know how successful the time-travel series would be. The role famously went to Eric Stoltz before he was dropped, mid-filming, for Michael J Fox. A few alternate time lines to consider there.
Tom Hanks there is only one Forrest Gump !
...These movies I have to watch at least, 4x or more a year