Actually, there was a prototype from Season 1, "Silly Song Time".
The identifiable members involved
Jim- Hippie Grump
Frank-Little Jerry
There were three other hippie muppets, presumably wiggeld by Carroll Spinney, John Lovelady, and Caroly Wilcox. One looked like Roosevelt Franklin in a different shirt.
Little Jerry sat behind the drums, performed by Jim, singing " Spinning Wheel". He also appeared in a few crowd scenes, most notably Frank's little boy character demonstrating Forward and Backward, and getting trampled for his efforts.
It was neat, in those early days, how nothing was set in stone, different performers had Little Jerry on their arm. But once Jerry Nelson came along, he found his voice