Why didn't The Wellingtons record the revised Gilligan's Island theme song?

The original version of the Gilligan's Island theme song was recorded by The Wellingtons.

According to "Here on Gilligan's Isle", the second (and third) season version of the song was performed by a group called The Eligibles.

User "supercat" asked in a comment on this question:

Do you know if the Wellingtons demanded a per-show royalty, or if there was some other reason they were used for the first season but not the second? Until I watched the show on DVD, I would have guessed the later theme started in a lower key; I was surprised to find the difference stems purely from the different singers' voices.

Why weren't The Wellingtons used for the later season recording(s)?

soundtrack gilligans-island

Best Answer

According to this comprehensive page about the show:

The theme [...] was recorded by "The Wellingtons", a folk-singing group (who later went on to record "The Ballad of Davy Crockett" for Disney, and appeared on GI as "The Mosquitos", the rock group that came to the island to get away from civilization). The original lyrics, "... and the rest" [which] were used because of clauses in Tina Louise' contract (her name/face had to appear last in the opening), were replaced by "... the Professor and Mary Ann" after the first season, though this time the song was sung by another folk group, "The Eligibles" -- the Wellingtons were unavailable due to work in Las Vegas at the time.

Also, the fact that the Wellingtons were credited but the Eligibles weren't suggests that it was not only easier but also cheaper to re-record the theme song with them.