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Meets Molly Cule Cracks a Yolk Goes to Mussel Beach

Cracks a Yolk is the second episode of the fourth season of The Magic School Bus. It is about eggs.


Dorothy Ann is taking care of a chicken egg and becomes impatient when it has yet to hatch after she accidentally lost Mr. Ruhle's Rhode Island Red rooster, Giblets. A flashback shows her promising him she will take good care of him and he flies away. When the scene fast-forwards to the present, she gets impatient and the class is eventually reported to Mr. Ruhle's office. So she decides that they should tell him the truth and that they are getting him a new one by hatching it from an egg. He, however, takes this as a joke and decides to play along. They tell him that they went to a farm replete with Rhode Island Red chickens and that the farmer let them get an egg as long as the chickens didn't escape.

Another flashback shows the class coming across a pen with roosters and hens inside. Ms. Frizzle guides the class into it, where they get pecked by the roosters and eventually run out. Dorothy Ann comes across one with only hens inside and decides that they should get the egg from it. She walks inside and grabs one from inside the henhouse. But she trips, it flies out of her hand, and cracks against a pan Liz holds out to catch it. Dorothy Ann runs out of the pen and tells Ms. Frizzle that it was going to be Mr. Ruhle's new chick. To find one with a chick inside it instead, Ms. Frizzle has Liz use the bus to shrink and cause them to fly inside a hen.

Back in Mr. Ruhle's office, he finds it hard to believe the class actually went inside a hen in search for an egg. Dorothy Ann continues her story, stating that they started in the ovary.

Back in the flashback, the class find themselves inside the ovary, where Ms. Frizzle explains to them that is the place in which the eggs start ticking. They then notice big, white spots on each of the orange balls in there and Ms. Frizzle explains that they are the ovums, the most important part of the eggs as they're half of what starts one. Just then, a yolk falls out of one of the balls, and they slide down a tube Ms. Frizzle says is called the oviduct, with the yolk trailing behind. Dorothy asks where they're going, to which Carlos jokingly states wherever yolks go when they "Eggs-it the ovary". They land right on top of the yolk, which continues to slide down the oviduct, and they notice it get covered with white and get tangled with some stringy rope-like substances.

Back in Mr. Ruhle's office, the class tells him that a layer formed around the yolk and white and swelled up into the shape of an actual egg. He then learns that it is exactly what happens when one is completely formed.

As Dorothy Ann continues telling the story, the class notices solid stuff forming around them until everything gets covered in a hard shell. They search for a chick and comes across the ovum, meaning this egg won't hatch into Mr. Ruhle's chick either. So Dorothy Ann decides that they should search for another one immediately.

Back in Mr. Ruhle's office, he finds it very hard to believe that the hen laid an egg with the class inside it. Dorothy Ann tells him that she did, and they would still be inside it, had it not been for Liz.

In the story, Liz steals the egg out of the hen's nest and uses a flashlight to see the class inside it. She runs out of the pen, cracks the egg against her head, they slide off, and return to their normal size. Phoebe informs them that the egg they were in came from the hen pen and Dorothy Ann then learns the other half of the chicken is the rooster and that, like almost all animals, it takes a mother and father to create a child. They walk into the rooster and hen pen and learn the hen makes the egg while the rooster adds his part of it before it grows into a chick. So Dorothy Ann acquires one from a nest and they take it back to school. En route, they wonder if only the hen's half is inside the egg and no rooster came along on time. So Dorothy decides to have Ms. Frizzle shrink her to get inside it. But when Arnold tells her that he would rather do so than face Mr. Ruhle, Ms. Frizzle shrinks him instead and he ends up inside the egg. Back in the classroom, he is searching for a chick and comes across the ovum.

The next scene shows the rest of the class inside Mr. Ruhle's office as Dorothy Ann finally concludes the whole story and he, having enough of this, tells them he wants his old or new chicken immediately. He also adds that it takes three weeks for one to grow, much to Dorothy Ann's horror as it will not do so in time, realizing she's doomed!

Back in the classroom, Dorothy Ann explains the situation to Ms. Frizzle and Arnold, who is still inside the egg, informs that the chick just got started. To make it grow faster, Ms. Frizzle transforms the bus into a hen and speeds up time to cause the chick to grow quicker. Arnold then notices that it is growing a head and eyes and Ms. Frizzle tells him that it is called an embryo. He then realizes that its heart is beating and blood is flowing through the yolk. The class arrives back in the classroom, and Phoebe is told to tell Mr. Ruhle everything Arnold says is happening inside the egg using a tape recorder. She explains it all to Mr. Ruhle as the embryo grows arms, legs, and even feathers. As it gets bigger, the egg finally hatches and the chick (along with Arnold) breaks out. Dorothy Ann was so happy that she would not get into trouble!

Liz uses the port-a-shrinker to return Arnold back to his normal size, and Dorothy Ann shows him the newly hatched chick. Out of gratitude, she kisses him, causing him to blush. Mr. Ruhle arrives in the classroom just in time to see the chick, and Giblets also arrives back, much to their surprise. Mr. Ruhle believes it was all a joke and guesses that they were just only hatching the egg the whole time to show him what they learned.

Ms. Frizzle lets Arnold and Dorothy Ann keep the chick (which Arnold names Arnold Jr.) and she concludes, "You can count your chickens before they long as you know what kind of egg they've been in," causing everyone to laugh.


  • The first kiss between the class happens when Dorothy Ann kisses Arnold to thank him for getting the chick to hatch and for saving her from getting into trouble with Mr. Ruhle. Arnold proceeds to blush due to this.
  • Wanda wants to name the chick "Yolkahontas" after the historical figure Pocahontas.
  • During the scene inside the hen's reproductive system, Ralphie's cap is on his helmet.
  • This episode compared to others depicts the field trip in a flashback. This isn't the only time this happened; "The Frizz Connection" tells the beginning of the field trip in a flashback as well.
  • Going by production order, this is the 1st episode of Season 4. It is the 16th switched to production order in the order used on streaming platforms. This episode was also completed on August 12, 1997.
  • Going by airdates, this is the second episode of Season 4.
  • The line "take chances, take aim, and get messy!" from this episode is used in the 1998—2002 FOX KIDS promo for the original series.
  • Arnold Jr. is the fourth class pet, preceeding the hamster and proceeded by Ratney.
  • This is the second episode to credit Paul Winfield.


  • In the scene where Dorothy Ann says "Thank you!" to Arnold, she's holding the chick in her left hand, but in the next shot where she kisses him, it is in her right hand.
  • When Mr. Ruhle points out how hard it is to believe that a hen laid an egg with the class inside, Arnold is among them, although he was actually inside the egg with the chick at the time.
  • If the viewer pays close attention to the students when Liz cracks the egg on her head, Carlos' suit is red.
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