I remember reading Ed O’Neill (Al Bundy on Married With Children) say that shortly after the show ended he got a serious role in a stage play. But when he walked on stage the first time, the whole audience cracked up laughing. “Al” was too big to overcome - I suspect Russell Johnson and the rest of the Gilligan’s Island crew had the same problem later in their careers.
Ginger Grant did a deodorant commercial after the show ended, IIRC.
Tina Louise was very bitter for years about how “Gilligan’s Island” ruined her ability to get serious roles.
(Then again, Charles Bronson felt the same way in later years about his “Death Wish” series.)
It's not uncommon. Every time I saw Alan Alda in anything, he seemed like Hawkeye Pierce to me.
Rob Reiner questioned the success of "All In The Family" until he went to see an old film of Julius Caesar where Carroll O'Connor happened to be playing the role of Brutus. When it came time for the assassination scene, folks yelled from their seats "Get 'im Archie!" and he knew the show was having an impact.
One of my favorite films is "Fail Safe" where up and coming actors Walter Matthau, Dom DeLuise and Larry Hagman all played serious roles before each had become famous for comedy and it was odd to see each of them not playing for laughs.
Finally, Groucho Marx would relate how angry it made him when ordinary people would not take him seriously. They just presumed everything he said was some sort of joke and would laugh at him. What a curse to have.