second banana

noun2

1. •
   (informal) A comedian who plays a secondary or supporting role, especially as straight man and traditionally in vaudeville or burlesque theatre.

   • He grew disenchanted with playing second banana and never getting credit for the laughter.
2. •
   (informal) A person who serves in a supporting, secondary, or subsidiary capacity; an assistant.

   • The plumber left his second banana behind, to finish installing my new sink.