From Muppet Wiki

Ferlinghetti Donizetti is a poet on Sesame Street. His name is inspired by 1950s beat poet Lawrence Ferlinghetti. He is a self-proclaimed rhyming pro.

Ferlinghetti appeared most prominently in "Rappin' Alphabet," which also features Grover as a break dancer. He was later seen in the framing story for Getting Ready to Read, appearing in Big Bird's Nest to assist with some reading skills.