Mary Louise is a little girl Whatnot who was most often seen on The Muppet Show performing alongside frogs in musical numbers such as "I'm in Love with a Big Blue Frog" and "Never Smile at a Crocodile," primarily during the first season.
In episode 208, she auditioned for the show by singing a duet with her friend, who was (not surprisingly) also a frog. After they're hooked off the stage, Mary Louise returned to audition twice more, under the names Carrie Louise and Terry Louise. All of these attempts were unsuccessful, in part due to Miss Piggy's explicit protestations that she's the only one who can sing with frogs on the show.
- The Muppet Show
- Episode 103: Joel Grey ("Comedy Tonight", At the Dance, performed by Eren Ozker)
- Episode 104: Ruth Buzzi
- Episode 108: Paul Williams ("I'm in Love with a Big Blue Frog," performed by Fran Brill)
- Episode 109: Charles Aznavour
- Episode 114: Sandy Duncan ("Never Smile at a Crocodile," performed by Rollie Krewson)
- Episode 115: Candice Bergen
- Episode 120: Valerie Harper ("Searchin'")
- Episode 122: Ethel Merman
- Episode 208: Steve Martin ("Swanee Ribbit," "Tie a Yellow Ribbit 'Round the Old Oak Tree," and "Old Man Ribbit," performed by Louise Gold)
- Episode 316: Danny Kaye
- The Muppet Movie ("The Rainbow Connection" Finale)