Originally, a second actor was hired to do the puppeteering and voice of Rusty the Rooster, but when that didn't work out, Rod Coneybeare was asked if he could handle both puppets at once and ended up doing double duty for the show's entire multi-decade run.
The musicians that provided the theme did not sign off on it being recorded once and being re-used from tape. As a result, they got paid to play it at the front and end of every episode that was taped.
The periodic musical episodes, where other creatures were brought in to play other instruments, with Rusty on guitar and Jerome conducting, were often played behind the scenes by major musicians, including Moe Kauffman. Jazz and Classical arrangements were common.