Once again, Ms. Frizzle gets her class right in the "thick" of things--this time, they're right in the thick ooze of an underwater volcano's magma chamber! As Arnold and Carlos watch from a raft above, the Magic School Bus "erupts" with the magma and lava, and lands atop a brand-new island!

The class needs a new mascot for their soccer team, the old mascot being so old that nobody even knows what it is anymore. Phoebe is convinced it should be the butterfly, but obviously the rest of the class doesn't agree with this. Janet (from The Magic School Bus Lost in Space) shows up again and convinces the class that their mascot should be the "Bog Beast." Since nobody seems to know what a bog beast is (that's probably because they don't exist), the Friz takes the class on a trip to the swamp to find out. Somehow they learn a lot about butterflies.

In order to find Liz, their missing lizard, the kids in Ms. Frizzle's class become reptiles themselves and discover what it's like to be cold-blooded.

When the principal, Mr. Ruhle (Paul Winfield), has to go away for a few days, he leaves his beloved chicken, Giblets, in Dorothy Ann's care. Unfortunately, the minute Mr. Ruhle is out the door, Giblets flies away. How will DA ever find another prized Rhode Island Red to replace Giblets? Where do you get chickens anyway? And which comes first, the chicken or the egg? The next thing DA knows, Ms. Frizzle and the class are on a field trip to see how eggs are made "from the inside out"! But will this egg have everything it needs to become "Giblets the Second"?

In the TV show "FLEXES ITS MUSCLES," Ms Frizzle takes the bus (and class) to R.U. Humerus' extraordinary Body Shop for repairs -- but Ralphie seizes the opportunity to build a robot to do his chores. The class joins in and they discover how bones, joints and muscles work together to help us move. But they do the job a little too well, and the Ralphiebot starts to take over. Can Ralphie stop the robot before it's too late?

Arnold's dream has come true. He doesn't have to go on a field trip! Ms. Frizzle lets him stay behind with Liz. But when Arnold accidentally swallows his miniaturized classmates, he becomes the field trip! Better than an action park, Arnold's digestive system is full of twists, turns, and surprises.

Guess who's selected to give an exhibition of a slam-dunk during half time of the big basketball game? Phoebe! The problem is Phoebe can't jump high enough. "If only gravity didn't pull on me!" she moans. Never one to be tied down, Ms. Frizzle sends the class into space and turns the Bus into a planet - with adjustable gravity! Basketball's a snap with low gravity and a riot with no gravity at all, but when there's way too much gravity, things get really heavy! With Paul Winfield as school principal, Mr. Ruhle.

After the illuminating light show at Walkerville's old theatre, Arnold's bossy cousin Janet claims she could put on a much better show. Nobody believes her until Janet and Arnold mysteriously disappear. Ms. Frizzle leads her class into the darkened theatre to look for them. To shed some light on the problem, the kids become beams of light. Then, to their great shock, they see Arnold's ghostly image floating high above the empty stage! Is the theatre haunted? Is this just one of Janet's tricks? Or have they all been "Frizzled"?

The Magic School Bus goes into show business when Keesha directs a movie about social animals for the school science fair. The class visits the inside of an anthill to observe their "characters" at close range and discovers that each ant performs a vital job for the survival of the colony.

It's Valentine's Day and the class is selling light bulbs. When they stop at Ms. Frizzle's house to sell her one, they find that her battery-operated doorbell doesn't work. While looking for Ms. Frizzle to tell her the doorbell's broken, Wanda overhears her teacher talking on the telephone. "Ms. Frizzle has a boyfriend," says Wanda, "and he's on his way over to see her! We've got to fix the doorbell or she'll never know he's here!" But first they have to figure out how the doorbell works...

Arnold and Keesha are in trouble when they forget an assignment to bring in "two things that go together." A soggy shoe and a tunafish sandwich, all they've got, lead to an ocean field trip in search of the connection between these two unlikely objects.

When Phoebe tries to grow a big vine for her school's production of Jack and the Beanstalk, all she ends up with is a stunted little sprout. To help out, Ms. Frizzle turns her into a real vine. But to grow tall, Phoebe needs to figure out how plants eat - fast! To unearth the amazing ways plants make their own food, the Friz and the kids shrink down and dig deep in a quest to root out the facts!

Ms. Frizzle's class arrives early to open the school for Mr. Ruhle (Paul Winfield). But there's so much to do! "There must be a way to do all of these chores without actually doing them," says Carlos. The school handyman, Mr. McClean (Malcolm McDowell) is in total agreement. Enter Mr. Ruhle's new computer and Mikey, Carlos' whiz kid brother, who programs it to do all the chores! But when Ms. Frizzle shrinks Mikey and the class and sends them inside the computer for a guided tour, everything goes haywire. The only person who can fix the problem is Mikey - and he's just landed somewhere between the CPU and the hard drive!

It's Ms. Frizzle's birthday, and a field trip to the bakery seems perfect... until the bus' shrinker-scope goes on the fritz, and the class experiences chemistry first hand as they get baked in a cake!

The debate is intense: Should Walkerville get rid of the swamp by the river and replace it with a fantastic new shopping mall or build the mall somewhere else? Carlos, representing his class, is given the thankless task of persuading the town council to keep the smelly old swamp. If he loses the debate, he'll lose to Arnold's pesky cousin Janet! The kids learn that the swamp is an important habitat and natural water filter, but the council's not convinced until... FLOOD!!

In the TV show "GETTING ENERGIZED," the class plugs their Double-Trouble Wheel of Wonder, the hottest ride at the school carnival, when their electricity fails. No electricity, no ride! Carlos' younger brother Mikey helps them discover that there are other sources of energy besides electricity. Using wind, water, the heat of the sun, falling rocks, and their own muscle power, the class gets the Ferris wheel running.

It's the night of the rock lovers' annual Granite Awards, and Arnold is about to become the first kid ever to win the coveted Rocky Award. He's so excited, all he's been able to eat for weeks are "Seaweedies" - and lots of them! When he arrives for the big event, he's totally nervous and totally...orange! Once the class determines that the orange isn't on Arnold's skin, they shrink down to explore what's underneath. They discover that his whole body is made of living cells - and they're all orange! But where is the orange coming from... and how can they make it go away?

"We got assigned air, and it's not fair!" The only contribution the kids in Ms. Frizzle's class have made to the Walkerville Space Capsule is an empty jar. "It's not empty," argues Keesha. "It's filled with air!" "But air doesn't do anything!" wails Ralphie. They discover that's not so when the bus shrinks and gets stuck inside the jar - and the class finds that their only hope for escape is... air!

The class' garden is going to be featured on the cover of PLANT IT! magazine. But Phoebe's garden plot is glaringly empty. Always eager to help, Ms. Frizzle shrinks the bus to the size of a ladybug, and the class is off and flying to Phoebe's old school to find a plant.

Ralphie wants to catch salmon to serve at the annual school picnic, but he can't find any at his favorite fishing spot. Where could all the salmon have gone? The kids are soon "Frizzled" inside a salmon bus that has an uncontrollable urge to head upriver. "Wait!" Ralphie cries. "We'll be late for the picnic!" But the salmon bus won't stop. Using its sense of taste and smell, it swims the long journey to a shallow freshwater stream miles away. Why has the bus, which thinks it's a salmon,gone to all this trouble?