"Inside Ralphie" is the third episode of Season 1 of the animated children's series The Magic School Bus. It originally aired on PBS on September 25th, 1994.
It's Broadcast Day and the class is counting on Ralphie to help them come up with an idea for the two hours of live television they're doing. The trouble is that he's sick, judging by his coughing, so his mother, Dr. Tennelli, won't let him go to school. So she calls Ms. Frizzle to tell her he won't be able to come. So instead, Ms. Frizzle takes her class to Ralphie's house.
When Ms. Frizzle says that there is an amazing battle going on inside him, the class decides Broadcast Day should be about whatever is making him sick, prompting Arnold to say "I think Ralphie shouldn't have stayed home today." They go back to The Magic School Bus, making him believe they are leaving him. It later returns as a shrunken helicopter through his window. Ms. Frizzle tells him to say, "Ahh!," and it enters his mouth, approaching his red and swollen vocal cords, but he coughs, sending it flying out. Afterwards, it enters via a cut on his leg, to which Carlos jokingly says "It's a shortcut! Get it? Short cut?" causing the other students to groan "Carlos, yuck!". The Magic School Bus travels up his bloodstream to his throat. While watching a video of his bloodstream, he notices that the blood inside is clear rather than red and that the cells and red and white blood cells and the jagged cells are called platelets, which help the body heal scrapes and cuts. Meanwhile, Dr. Tennelli returns and notices the television. She remarks that the stuff on it is "remarkably realistic".
As The Magic School Bus enters the throat tissue, the students attempt to do the report. Ralphie and his mother watch this on television and notice that bacteria is destroying his throat cells, making him sick. Just then, the white blood cells come around and eat it. Unfortunately, it multiplies and begins chasing the students. Dr. Tennelli then turns off the television and tells Ralphie that the best cure for a bacterial infection is complete rest. As she leaves, Liz turns it back on and the inside story continues, where the medicine Dr. Tennelli gave Ralphie earlier destroys the bacteria. The white blood cells also see the bus as a threat since it's covered with antibodies and attempt to devour it. The others call for help, but Ralphie doesn't notice since he's sound asleep. The bus barely manages to escape from the white blood cells' grip and ride off, with the white blood cells chasing after it. They make it to Ralphie's nose, and he wakes up just in time to listen to the report on television.
The bus travels up his nose and Ralphie says “That’s the inside of my nose?” in surprise and adds “Weird”. After Liz tries tickling his nose with a feather, Ralphie initially tells her angrily that he’s trying to think, but then says, “I get it — I got to sneeze them out” but then looks puzzled while adding “But I don’t feel like sneezing.”
Liz solves that problem by sprinkling black pepper in his face. The students, still small, are now back in his room and interview him. They tell him that his body is built to keep out things such as germs, his throat is sore because of his body sending extra blood there to fight off the infection, and the white blood cells almost ate the bus because his body thought it was bacteria. They also tell him that his body was doing all this to protect him.
As he finally gets some rest, the other students hop on the bus and leave through the window.
Ralphie: "How can anything that smells like grape shoe polish help my body get well? Ugh!"
Dr. Tennelli: "It will if you take one teaspoon three times a day. And don't forget to shake well before using."
Ralphie: [shakes] "Like this?" (Salsa music plays)
Dr. Tennelli: [rolls eyes] "Even your jokes are sick."
Ms. Frizzle: "Ralphie, say 'Aaaahh!'"
Ralphie: "Aaaaaaahhhh--" [the bus shrinks] "AAAAAGGGGHHHH!!"
Ralphie: "How are you gonna get the inside story if you can't get inside?" [notices his bandage] "Wait a second...I got it!" [takes the bus to his cut] "Look at this! Is it just me? Or does this say 'This Way In'?" (unpeels band-aid to show his healing cut)
Carlos: "It's a shortcut! Get it? 'Short cut'?"
Students: "Carlos! Yuck!"
Arnold: "I'm gonna try to get an exclusive interview with these two bacteria." [bacteria multiplies] "I mean 'four bacteria'." [bacteria multiplies even more] "I mean 'eight bacteria'? Hey, guys! They're multiplying! Help!"
Arnold: "I think Ralphie shouldn't have stayed home today!"
Arnold: "I'm the one who should've stayed home today."
- The medicine Dr. Tennelli gives Ralphie is most likely an antibiotic.
- The white blood cells' would-be consumption of the bus is a reference to Fantastic Voyage.
- Ralphie's last name is revealed when Wanda recognizes who Ms. Frizzle is talking to when she answers the phone.
- This is the second episode to take a field trip inside a human body and the first episode to do so other than Arnold's which was first seen in For Lunch.
- Ralphie is the first of Ms. Frizzle's students to get sick. The second is Dorothy Ann in "Sees Stars". However, Ralphie's illness is more prominent as this one's about the immune system and germs while "Sees Stars" is about stars, and it wasn't explained how Dorothy Ann was sick in the latter.
- The bacteria causing Ralphie's illness looks like streptococcus. "Coccus" means "ball" and "strep" means a long chain. Therefore, it's likely that he had strep throat.
- This is the only episode in which the class (except for Ralphie and Liz) doesn't return to normal size at the end.
- This is the second time the bus shrinks, but the first where it shrinks with Arnold and without Ralphie.
- The William Tell Overture plays in one scene where Ralphie's medicine destroys the bacteria.