"The Tale of The Frog Prince": Candy Clark plays both Queen Gwynneth and Candy. Roberta Maxwell plays both Queen Beatrice and Griselda. Donovan Scott plays both Hendrix and the French chef.
"Rapunzel": In the first part of the story, Shelley Duvall and Jeff Bridges play Rapunzel's ill-fated parents; in the second part, they play the now-grown Rapunzel and the prince she falls in love with.
"Jack and the Beanstalk": Mark Blankfield plays the old man who gave Jack the beans, the "fairy" that Jack meets while climbing the beanstalk, and he narrates the episode.
"Hansel and Gretel": Joan Collins plays both the evil stepmother and the wicked witch.
"The Princess and the Pea": Beatrice Straight and Pat McCormick play the couple in the museum and Queen Veronica and King Fredrico. Tim Kazurinsky plays the museum guard and the fool. He also narrates the episode.
"Aladdin" has James Earl Jones playing both the Genie of the Ring and the Genie of the Lamp. He also narrates the episode.
Actor Allusion: In The Boy Who Left Home to Find Out About the Shivers Christopher Lee (at the time, most famous for playing Dracula) play's Dracula's son Vladimer, complete with a scene where he rises from a coffin in a haunted castle.
Edie McClurg, who played one of the mean girls in Carrie, which is often viewed as a horror retelling of Cinderella, plays one of Cinderella's stepsisters.
All-Star Cast: The concept of the show arose from Duvall, during the Popeye shoot, musing on what it would be like if her co-star Robin Williams played the Frog Prince. The very first episode was indeed, "The Tale of the Frog Prince", with Williams as the title character, and Teri Garr as the princess. From there, every episode has at least a name performer in the lead, and usually a substantial contigent of A and B-list stars in the supporting roles.
What Could Have Been: David Bowie was cast as the title character in "The Pied Piper of Hamelin", but scheduling conflicts led to Eric Idle taking over the part — resulting in an effective Playing Against Type dramatic performance for the comic actor. (Idle previously wrote, directed, and narrated "The Tale of the Frog Prince", one of the lightest episodes of the series; by comparison, "Pied Piper" is one of the darkest.)