Skit Format
Skits that paired Lefty with Ernie often began with Ernie walking or otherwise minding his own business, Lefty calling out, "Psst! Come here!" and a startled Ernie responding, "Who me?" Lefty would then begin to make his sales pitch for an esoteric item, such as a letter of the alphabet, a box or a snowman. Often, Lefty would give a silly description of said item's "usefulness" so as to trick Ernie (who he hoped was naive and unwary) into buying. However, Ernie usually got the upper hand, frustrating Lefty; at one point, he shakes his head and sighs, "Why me?"
During those skits that paired Lefty with Ernie, Lefty was notorious for looking repeatedly right and left to make sure no one overhears him. For that reason, every time Ernie talked too loudly (which he often did), Lefty would utter a long "Shhhhh!" which usually made Ernie shake like a leaf and sometimes even caused him to intimidatingly crouch down.
Lefty was also seen in skits with a character known simply as "The Boss" (a Fat Blue Anything Muppet). These skits were often set in a dark alley or abandoned warehouse, and involved activities such as trafficking carrots (for a pet rabbit) and theft of items such as the "Golden AN" and reciting the alphabet.
As such, the educational benefit of the "Lefty" skits seemed to be his descriptions of his wares. For example, in addition to telling about the words spelled with the letters he sold, one of his skits talked about the uses of air — breathing, playing instruments, and blowing up balloons.
Read more about this topic: Lefty (Sesame Street)