When the pilot episode for Bonanza was originally run, it included three of the Cartwrights singing the words to the theme song (Pernell Roberts wisely tended to the horses!) The audience reaction was generally to role on the floor laughing, as the words were comical and the picture of these cowboys jumping on their horses singing them ridiculous. For the rest of the series the familiar instrumental version of the song was used, and it is even heard in the re-runs of the pilot that I have seen. So for those who have never heard the lyics to Bonanza, here they are:

(Little Joe) I've got a flair for women everywhere --
Bonanza!
(Hoss) Bonanza! (Barks and howls)
(All three) I'm not afraid of any pretty maid -- Bonanza!
Bonanza!
But when I give a kiss to any little miss
She'll learn a lot from me
(Ben) I'm not afraid of any pretty maid -- Bonanza!
(All three) Bonanza!
When I give a kiss to any little miss
She'll learn a lot from me
Hair of brown, hair of gold
I take what I see
We're not a one to saddle up and run -- Bonanza! Bonanza!
Any one of us who starts a little fuss
Knows he can count on me
One for four, four for one
This we guarantee
We got a right to pick a little fight -- Bonanza! Bonanza!
If anyone fights any one of us
He's gotta fight with me!