Michael Caine as Colonel Caine?
from imdb trivia
Sir Michael Caine was originally offered the role of Colonel Colin Caine. If Caine had played the part, he would have portrayed a character with the same last name as his own
Caine probably would've been better off doing Lifeforce over the comedy movie he did around the same time 'Water' which was pretty awful and completely forgotten. at least LF became like a cult scifi hit but would've been another one of Caines 80s bombs on the level of Jaws The Revenge.(and the press probably would've tried to pin the blame on Caine lol). It would also have been Caines proper scifi film before he got into doing them later in his career Children of Men, Prestige, Inception, Tenet (and it would've meant he starred with both captains of the Enterprise)
I'm guessing had he accepted they'd have changed the name share