 In the credits, Russell Johnson (I) (qv) and Dawn Wells (qv)  were relegated to being simply "The Rest". That changed in the  second season when Bob Denver (qv) demanded that they be given an  equal share in the credits, thus changing the lyrics to "The  Professor and Mary Ann." Sherwood Schwartz (qv), who composed both  themes, has said it didnt occur to him the Professor and Mary Ann  would turn into prominent characters.