Anne B. Davis. The perfect sidekick. Schultzy and Alice on the Brady Bunch. She had a great, expressive face.
Just googled Gabby Hayes (does that sound a bit risque?). Edgar, you're right. He was Roy Rogers' sidekick in the movies.
I was gonna draw the line and say no animal sidekicks (Trigger). But then I remembered Mr. Ed. Of course the question here is, was Mr. Ed the sidekick? Or was Wilbur Mr. Ed's sidekick? Why is life so complicated?
The Avengers, although I'm not sure which character qualifies as the sidekick.