Gilligan's Island: Up at Bat (1966)

Originally aired September 12, 1966. Gilligan is bitten in the neck by a bat and fears he will transform into a vampire as a result. Gilligan's troubled sleep is haunted by a dream that he is indeed a vampire living in a European castle in 1895 where unsuspecting travelers and a famous detective and his doctor assistant appear at his doorstep. (Synopsis from IMDB.com)