Don't you know?
That's Ernie and Burt. They're characters on a PBS children's program that begain in the early 1970s. Ernie is, obviously, a metaphor for the devil, and Burt is symbolic of The Man keeping the working class held down.
Censors were quick to pick up on their sexual ambiguity and racial dischord: Burt is yellow/ Ernie is orange (actually "Saffron"). That's why they changed the design of their shirts.
There message has shifted over the years from one of "numbers/counting" to the "letters/alphabet".

The banana is from episode #437, but that's another story altogether.