From Muppet Wiki

Hair is a musical written in the 1960s during the anti-war movement.

References

• The Muppet Show episode 316 features the song "Aquarius" from the musical. In parody, a group of Whatnots appear throughout the number with lengths of hair that grow as they reach the end of the song.

• In Sesame Street Episode 4128, Zoe becomes obsessed with having a head of hair. As such, she imagines herself in a music video with Gabi, Miles, Elmo and a bottle of shampoo. The throwback to the 60s and the emphasis on hair is a reference to the musical, as they sing "Take Care of Your Hair."

• Sesame Street Dinner Theatre spoofs Hair as "Pear" in Season 38.