- John White as Michael Webster
- Kristen Bone as Tara Webster
- Cynthia Belliveau as Mrs. Webster
- Larry Mannell as Mr. Webster
- Kyle Fairlie as Michael Webster at Age 6
- Alyssa Gebert as Mona
- Jake Roberts as Anthony
- Sam Hilwi as Josh at 12
- Brandon Smith as Josh at 6
- Christopher Chung as Henry at 12
- Michael Ho as Henry at 6
- Steve W. Smith as Scary Man
- Zachary Brian McQuaid as Michael at Age 3 (uncredited)
Michael Webster's life is pretty good, except for one tiny detail: Tara. Tara is Michael's bratty, obnoxious, impossible little sister. She gets Michael into trouble with their parents, embarrasses him in front of his friends, and is always playing mean tricks on him. Michael has had it! So when Dad comes home with an eerie old cuckoo clock and tells Tara not to touch it, Michael sees his chance to get even. What Michael doesn't realize is that the cuckoo clock has mysterious powers of its own, and his little prank is about to set back the hands of time . . . forever!
Differences from the book
- While in the televised version Michael Webster experience being 12, 6 (on his sixth birthday), and a baby in the past, the book has him experience a much longer time reversal, first going into 12, 3rd grade, 2nd grade, kindergarten, nursery school and being a baby.
- Michael does not experience getting beaten up by Kevin Flowers or being seen in his underwear.
- Michael's dream is different. It is not of a scary version of his birthday. Instead, it is the clock with Tara's head for a cuckoo chasing him.
- The first time when Michael's father tells Tara not to touch the clock, the father is also visibly more upset than in the book.
- Michael's father is a lot angrier at finding him at Anthony's Antiques than in the book. Later on, when he was brought back to the present it is the actual present, and he gets the same scolding from his father that Tara got earlier. Michael being happy to see his parents again catches his father off guard.
- In the book, Michael notices that 1988 is gone from the clock when his father shows him the cuckoo clock and mentions that there's a strange design flaw on it. In the TV version, Michael's father is the one who notices the missing 1988 year and laughs it off while Michael realizes that his mistake in 1988 led to his bratty little sister never existing.
- Tara's bedroom has become his father's office in the TV version. In the book version, it's Michael's bedroom.
- Michael does not mention having his arm broken when he was young in the episode.
- This, "The Haunted Mask", and "Werewolf Skin" are the only TV episodes to not be released on DVD. Though the episode is accessible through iTunes and Netflix.
- The second time Michael goes through his birthday, his mother asks him to help her with his cake. When he goes to her, you see they are outside. But the first time of Michael's birthday, they were inside.
- In the scene where Michael is dreaming, he opens the door to the room the cuckoo clock is in and begins to scream. But we hear the scream a split second, before his mouth opens.
- The first time when Michael's father tells Tara not to touch the clock, you see she has bangs on her forehead. But when she turns around to stick her tongue out at Michael, her bangs are gone.
- This episode, along with "The Girl Who Cried Monster", on their original premieres had a special opening theme in which there was a ten-second remix when R.L. Stine is walking through the grass with the briefcase. When the G passes the dog, that part of the music is played with a different instrument. There were also different scenes from the television show when the door opened.
- When Michael looks in the mirror at age 6, his scream and facial expression is exactly the same as Macaulay Culkin's scream in the Home Alone movies (and he also bears a resemblance to him).
- John White (Michael Webster at 12) played Steve Boswell in season two's "Haunted Mask II".
- When Michael is 6, his father reads him Norman Bridwell's "Clifford the Big Red Dog." Like Goosebumps, Clifford is also a Scholastic property.
- This is the only episode where the opening text is white instead of the normal green color.