"Axed by Addition" is the third episode of Goof Troop, and the first regular episode of the series.
P.J. gets Max to help him study when Pete says he'll be grounded forever if he fails tomorrow's big math test. When P.J. thinks he failed the test, Max helps him fake an illness so he can take him around town and live life to the fullest for his last day of freedom.
P.J. is studying for his math final, but finds it difficult to remember all the equations. Pete comes in asking how he is doing and tries to quiz him, only to confuse his son. Pete tells him that he had to "trudge through snow" just to get a good education and that P.J. "has it easy". He tells the boy that if he does not pass his test, he is grounded forever, much to his horror. P.J. then cries out for Max to come over to help him study for the test; preferring to do it the proper way rather than cheating. However, when Max asks a basic math problem such as "2 + 2", P.J. is sent into a mathematical tailspin and becomes hopelessly unable to answer without thinking too hard. Max then rigs a machine on P.J. that feeds him fudge bars if he gets a question right and slaps him with an egg if he gets a question wrong. Max puts P.J. through the rigorous training all through the night.
The next morning, P.J. cannot answer a question without it being math related and is traumatized at the mention of eggs and fudge bars. Believing that P.J. is trying to get out of taking the test, Pete kicks him and Max out of the house. Once at school, P.J. sits down to take the math test with Max's support. Upon starting, he immediately falls into a trance and cannot stop thinking about the previous night's ordeal. Afterwards, Max asks how the test went, but P.J. cannot remember as it is "all a blank". Thinking that he failed, Max decides to help P.J. out by having him fulfill one final day of doing all the things he's ever wanted to do.
Early the next morning, they make a list (Eat 200 Gorilla Burgers, watch all twelve Mutilator movies, ride down Hairpin Hill on a shopping cart, kiss Cynthia Snodfrew, and go on the three worst rides at Terrorland). Since it is a school day, Max gets the idea to make P.J. look ill and proceeds to apply makeup onto him to make him look like he has "Outer Mongolian Worry Warts" and "Peruvian Pussface". Upon entering P.J.'s room to wake him up, Pete goes into a panic and calls an ambulance to come bring P.J. to the hospital.
Max sneaks into the hospital past a grieving Pete who blames himself for his son's "condition". Once he manages to get the hospital staff away from P.J. he sneaks him out and the two boys take off. The surgeon, Dr. Howard, sees the leftover makeup (a piece of broccoli) and realizes that they had been tricked. He tries to tell Pete about what happened and shows him the list that the boys left behind. Misunderstanding the doctor and still thinking that P.J. is terminally ill, Pete takes off after the boys to beg for P.J.'s forgiveness for all the times that Pete had ever mistreated him.
Max and P.J. zoom through the streets, stopping by Gorilla Burger to get 200 burgers. They then barge into a video store and play all twelve Mutilator movies on fast forward. Then they head over the Hairpin Hill, from the top of which P.J. rides down in a shopping cart. On the way down the down, P.J. rides alongside Cynthia Snodfrew's car and leans over to kiss her, but he ends up kissing her dog instead. All the while, Pete drives closely behind and keeps running into a rather irate cop on a motorcycle. In the chaos, Pete's car is completely torn to shreds as he desperately tries to catch up with his son.
Eventually, the boys reach Terrorland and P.J. gets on the rides with Max telling Pete (who has finally caught up to the boys) to wait until 3:30 since P.J. is "contagious". Afterwards, everyone returns home with Pete cradling the tired P.J. when the phone rings. Pete answers it with Dr. Howard revealing that his son has "test anxiety" otherwise known as "faking". Pete flies into a rage and confronts the boys about what they had done and put him through. When P.J. brings up that he would have been grounded for life, Pete tells him that he was just exaggerating ("Do what I think, not think what I say!") and grounds him anyway. Later, Peg comes in with P.J.'s report card from the 3:30 mail and tells him that he got an A in math. Pete excitedly tells P.J. that he is going to take him out and do the things that he, ironically, had on his list.
- Jim Cummings: Pete, Gorilla Burger voice
- David Doyle: The irate traffic cop
- Bill Farmer: Goofy, Terrorland announcer voice
- Dana Hill: Max
- Rob Paulsen: P.J.
- Kath Soucie: Nurse, Cynthia Snodfrew, lady with baby
- Jim Staahl: Dr. Howard
- April Winchell: Peg
- Goofy only has a short cameo. He briefly passes the ambulance that comes to pick P.J. up.
- Douglas Twinkmeyer, Kathy, Melvin, and Bob all make non-speaking cameo appearances at the school in this episode.
- Max's watch has Quackerjack on its face.
- The hospital nurse uses the same animation model as Doris, the cashier of Norton Drugs seen in "Maximum Insecurity".
- When Max distracts the doctors from operating on P.J., he states, "Calling Dr. Howard, Dr. Fine and Dr. Howard". This is a direct reference to the classic Three Stooges short Men in Black where the nurse calls Howard, Fine and Howard (Moe, Larry and Curly) to the operating room.
- Error: When Pete crashes his car into the truck, his roof gets ripped off but the truck doesn't get damaged.
- Working title: "Fatal Subtraction"
- Continuity: In this episode, it is stated that there are twelve Mutilator movies. But, a mere three episodes from now, "Midnight Movie Madness" will declare the latest installment in the Mutilator film series to be the newly-released The Mutilator on Main Street: Part Seven, suggesting this episode to instead take place way after that one.
- In one shot, P.J.'s bare feet are shown while he's in his pajamas, contradicting the fact that his pajamas have heels and toes.
- In the shot below, P.J.'s bare foot is black respectively.