Marvin is taken in by the Formans, a quintessential American suburban family, who now have to hide his identity and help him live the life of a normal human kid. Unbeknownst to his human “parents” and to the chagrin of his human “sister,” Marvin sneaks out of the house to attend high school.
Marvin's ability to talk to horses inspires a plan from Grandpa to help him win big at the track. Meanwhile, Teri and Brianna come up with two inventions, The "Hairbandit," and "StickyBuds".
Marvin "fends for himself" and eats a huge amount of chocolate when a family meal is called off, and soon he develops an explosive toothache.
Marvin learns what an expiration date is, and he thinks that Pop-Pop will expire when he sees his driver's license. The day before Pop-Pop was supposed to "expire," he says that the bacon is going to expire in one day so Bob tells him to freeze the bacon to keep it fresh. So he freezes Pop-Pop. Marvin, Henry, Liz and Bob soon discovered that Pop-Pop was tricking Marvin so he can get whatever he wants. Upon unfreezing him, it is unveiled that Marvin tried to make a device to make Pop-Pop young again. But it backfired so he is now an elderly. He was about to die, so he asks Bob to make him a smoothie as his last wish. It is revealed that he only set his cloaking device to "Old Fart". Meanwhile Teri and Briana plot revenge on a boy who has asked them both on a date only to find out that the boy is actually a twin.
After seeing a bicycle with training wheels on them, Marvin asks for more money, so Liz says to Marvin that Teri has a job at Burger on a Bun. He goes in for the job, but takes it too seriously. That only got him to Assistant Manager. Taking the job too hard, he fired Teri. Burger on a Bun went downhill in quality, so Briana quit when Marvin kept on taking it seriously. This caused him to make the burgers in his own way. After people started leaving, Marvin Quit. But he spent all the money he made on Katy Perry tickets for Teri. Meanwhile, Pop-Pop and Henry find a suitcase Bill Gates lost 20 years ago and try to open it, only to find the suitcase itself is valuable.
Marvin begins to spend time with the popular kids at school and gets the cool reputation, but his new popular friends make him take the risk of breaking the rules and forgetting his best friend. Meanwhile, Teri obsesses over the unknown writer of the notebook she found at school.
When Liz forbids Marvin and Henry from seeing a scary movie, they disobey her and watch it anyway. After seeing it, the horrors from the movie come to life. Meanwhile, Teri tries to impress a boy by "accidentally" pocket dialing him and pretending to do exciting things.
Marvin and Teri go on a double date. After Marvin takes a picture of him and his date, Liz, Henry and Pop-Pop thought that the waiter is a Klerg.
When Marvin wants to try and pick a sports team to be active, he picks Basketball and soon discovers he has the gift and talent of playing it.
When Marvin sends the Forman family to a unknown planet by mistake, he must tell Brianna that he is an alien in order to save them. In the end, it turns out that the family was still on Earth.
Marvin needs a band to perform in "Battle of the Bands", so he uses a group of kindergarteners. Meanwhile the Forman family has a chili cook off and the loser has to eat their chili from Marvin's shoe.
Marvin finds a Klootonian egg and tries to raise it as a pet against Liz and Bob's wishes. Meanwhile, Teri tries to make everything perfect when meeting a U.S. senator.
Marvin uses a Calm Palm on Teri when she's over stressed about a fencing competition. Meanwhile, Henry and Pop-Pop want to play hockey in the house, but Bob and Liz want them to follow the house rules.
Marvin and the Forman family celebrate St. Glar Kai Day, but they also have to deal with federal agents who discover alien activity in their house.
Marvin accidentally steals one of Ben's precious comic books, and he must return it before Ben finds out. Meanwhile, Teri and Brianna think that Liz is reading Teri's phone text's.
Marvin joins a book club to spend time with his new crush; Marvin pretends to be sick to catch up on reading before a book club meeting. Meanwhile, Teri lets Brianna share her locker after a crime scene was done near her locker.
Marvin watches a bunch of Teen Party movies, and plans a party against Teri's wishes. Meanwhile, Liz, Bob, Pop Pop, and Henry fight a snowstorm to get to Henry's skating tournament.
Marvin's Klootonian uncle, Uncle Steve, visits the Formans. He threatens to take Marvin back to Klooton.
Marvin and Teri go to a Big Time Rush concert, but Big Time Rush got kidnapped by the Klerg, and so did Teri, after being mistaken for Klootonians. Now it's up to Marvin to save them.
