After freezing when Echo asks Adam to join her at the sci-fi convention, he creates a serum that will give him more confidence. Unfortunately it also turns him into a monster. Now Adam must wait for the effects of the serum to wear off, while trying to hide his monstrous form from Echo.
While returning a lost Rudolph to the North Pole, Adam unintentionally suggests Santa automate his workshop, which results in Santa firing the elves. The unemployed elves follow Adam back to Finnegan to have him put things right. Now it's up to Adam to find them a new job, or deal with their pint-sized wrath.
Adam has trouble getting some peace and quiet at home, so he decides to rent an apartment of his own. But when Derby, Echo, Slab, and Ivy all come over and want to use his new pad for their own purposes, Adam starts to wonder if home wasn't so bad after all.
When a new girl arrives at Finnegan, Derby wins her heart. But when it's revealed she is the daughter of his sworn enemy -- TV Pitchman, Preston Pickles - he is forbidden from dating her. Derby must find a way to pitch himself as good boyfriend material to the ultimate pitchman.
While experimenting with a white hole, Adam accidentally causes time in his classroom to move incredibly fast. As he works to solve the dilemma, he and Derby age sixty years over the course of twenty-two minutes. Meanwhile, Echo and Slab team up to stall Tater from entering Adam's class, which would cause the time vortex to spread throughout the school.
Adam is thrilled when Echo asks him on a date to the Magic Mansion, but his hopes for a real date are crushed when he finds out she invited everyone at school along. Adam's determined to get rid of the competition, making them disappear one by one using a mysterious magic cabinet. Meanwhile, Tater tries to become a member of the Magic Mansion, despite not knowing any magic tricks.
Adam realizes he and Echo don't have anything in common, so he decides to join a few of her favorite school clubs. But when Adam finds out that Finnegan has a secret club that Echo is in, he'll do anything to join.
It's Valentine's Day and Adam plans to go out with Echo - until she comes down with a nasty cold. Determined to save his night out, Adam creates a shrink ray, and shrinks himself and Derby to microscopic size. They venture into Echo's body to battle the virus. Then have to find their way out again.
ARTHUR returns to Finnegan with his new robot family and asks Adam to babysit his "grandkids." Adam agrees and tries to impress Echo with his parenting skills, but soon realizes that dealing with kids is not as easy as it looks.
Adam, Echo, Derby, and Slab wake up the morning after Hallowe'en, having eaten so much candy that they can't remember what happened the night before. When they discover Derby's wallet is missing, they must retrace their steps, asking help from Ivy, Tater, Dang, and Mrs. Byrne along the way.
Upon discovering that the mythical giant chicken monster, Sasquawk, has been captured by legendary monster hunter Malcolm Hastings, Adam frees her. But Sasquawk develops a crush on her rescuer, and, feeling threatened by Adam's relationship with Echo, kidnaps him. Now Echo must save the day before Malcolm hunts both Adam and Sasquawk down.
After Adam and Tater struggle to find budget cuts at Finnegan High, Cyclops Foods buys the school and turns it into a product-testing facility. But when a faulty product transforms Derby into an actual cyclops, Adam must find a way to reverse the effects and save Finnegan.
When Adam discovers Ivy has tickets to the sold-out music festival Echo wants to attend, he agrees to tutor Ivy in exchange for the tickets. Adam must now make Ivy a whiz in science, or lose his date with Echo.
After a bad date, Echo decides she and Adam should set each other up on a double date. Now, Adam must find a guy who Echo won't fall for. Meanwhile, Echo realizes she might just be the perfect girl for Adam.
Ivy invites the cheerleaders over for a slumber party, and Adam panics at the realization that Echo may discover a shrine exposing his true feelings for her. He plans his own slumber party to prevent Echo from entering the basement and learning the truth.
When a sci-fi movie comes to shoot at Finnegan, Adam is hired as the science advisor. He makes the movie so realistic that his interstellar beacon prop contacts real aliens... who arrive, and, in their first step to conquering Earth, kidnap Echo.
The Finnegan High time capsule is dug up twenty-five years prematurely and Adam panics when his love letter to Echo is discovered. Luckily, Adam's signature has been destroyed. But when a student claims to be the author of the letter and he and Echo get close, Adam must prove the student is lying, without exposing his true feelings for Echo.
Convinced that a bad first impression is the reason Echo doesn't consider him 'boyfriend' material, Adam borrows a time machine from his college professor, and travels to the past to meet Echo for the first time all over again. But after making the perfect first impression, Adam returns to the present to discover Echo now hates him. Learning that her anger stems from an incident at the Finnegan High talent show, Adam must head back to the past and make things right.
Adam returns from his latest trip to the past to discover that he has now been fired from his job, Echo has transferred to a new school, and Derby is the biggest pop star in the world. To make matters worse, the time travel device winds up in the hands of Preston Pickles, forcing Adam to once again do battle with his old nemesis in order to win back the device.
After creating a timeline where elephants have taken over the world, Adam finally accepts that he and Echo will never be together. He returns to his first day at Finnegan once more, to put things back as they were. But when his time machine runs out of juice at a critical moment, Adam is in danger of being permanently stuck in the past.
Adam and his mentor, Professor Fenway, try to convince Ivy to sign up for college by telling her about Adam's first day at Great Northern University. But, to Adam's chagrin, Professor Fenway's story involves an embarrassing glimpse into Adam's day as a fourth grader.
A TV news program comes to interview Adam about being the world's youngest high school teacher. To ensure the interview goes smoothly, Tater has dumped Echo, Derby, and Slab in a fake version of Finnegan High.
Adam and Echo struggle to keep their romance secret from Principal Tater. But when Derby discovers the truth -- and almost gives away their secret -- Adam plans to erase Derby's memory. Unfortunately, it's Echo's memory, including her love of Adam, that accidentally gets erased. Meanwhile, Ivy tries to convince Slab to ask her out, so she can reject him.
Adam must stop the new, teenaged science teacher, Mr. Kidd, from using Adam's own memory-erasing invention against him. If Adam fails, everyone's memories of him will be erased, and Adam will lose everything. Meanwhile, Ivy and Slab have to do a book report on George Orwell's 1984 ... But first, they have to figure out what it's about.
A Hollywood writer comes to Finnegan with the intention of making a TV show about Adam. But he is distracted by Echo, Derby, and Ivy, who all think they have better ideas for TV shows, starring themselves.
Dang is called back to Vietnam to take over for Master Ki as guardian of his village. The gang heads to Vietnam to try and convince Dang to come back to Finnegan for graduation. While there, Adam discovers an ancient scroll that points to the mythical fountain of youth, which if found, could make Master Ki young again, releasing Dang from his duties. But to find the fountain, Adam must go up against Echo who is trying to preserve the leaf monkey habitat.
While Adam and Derby explore a hidden, underground temple in search of the fountain of youth, Tater helps Echo learn about monkey behavior, and Ivy helps Slab prepare for his first ever cover model photo shoot. All roads lead to a confrontation with a local fancy hat factory owner, who has been keeping a secret from the villagers for generations. In the end, Adam gets the gang back to Finnegan, just in time for graduation.