Stepsister from Planet Weird (2000 TV Movie)
A teenager's life is disrupted when her mother falls in love with an alien.
- Teenager Megan Larson daydreams that her divorced parents will get back together, that she will be asked to sit at the popular girls' lunch table, and that Cutter, the boy she has a crush on, will ask her to be his girlfriend. Unfortunately none of these things are likely to happen.
Megan's mother Kathy is unconventional, often serving soup for breakfast. She works at a sports shop, and she and Megan both enjoy windsurfing. Cosmo Cola is also unconventional -- he and his daughter, Ariel, are from another planet. Cosmo was a Freedom Fighter and his wife was killed, which was why he and Ariel came to Earth. They are hiding from the evil emperor Svad, whose son Fanul was Ariel's boyfriend. Ariel begs to be allowed to contact Fanul but Cosmo forbids it.
Cosmo and Kathy meet when he tries to rescue her from windsurfing, thinking she is in danger. As she tells Megan, they instantly hit it off. Cosmo is funny, sweet, and very carefree, all of which Kathy finds refreshing. But Megan doesn't like the idea of anyone replacing her father. She is suspicious of Cosmo's claim that they are from the Yukon, since no one lives there.
Ariel doesn't approve of her father's romance with Kathy. She consults her neighbor, a medium named Serena Sue, but finds the woman to be silly. Serena is obviously interested in Cosmo. When he and Ariel are outside, she spies on them. She is startled when Ariel runs screaming into the house after a gust of wind occurs. Cosmo goes after her and assures her there is nothing to be frightened of. Ariel wants to return home but it is too dangerous. Cosmo likes Earth and he makes a good living selling diamonds online. Ariel cannot understand their value; on her home planet they are worthless stones.
Kathy invites the Colas to dinner. Megan is sullen and her little brother Trevor thinks Cosmo is probably an alien. When Cosmo arrives he gives the children an over-enthusiastic greeting and offers his contribution, a case of root beer. Unknown to the Larsons, Cosmo and Ariel need its carbon dioxide to survive. On their home planet they are not humans but gaseous bubbles.
Ariel is not with her father; she is hiding under the car because she is afraid of wind. The Larsons are puzzled and Megan is sent to retrieve Ariel. On entering the house, Ariel is afraid of the Larsons' dog. She grabs a bottle of root beer and runs into the bathroom. She emerges dripping wet because she had turned herself into a bubble in the sink. Megan doesn't believe her story of falling into the sink and takes her upstairs for some dry clothes. Ariel retreats in fear when offered Megan's blow dryer. Megan thinks it is because Ariel is vain about her hair. But in reality, hot air could prove fatal.
Cosmo piles toppings on his hot dog, including corn chips. Trevor copies him. Then Kathy and Cosmo announce their engagement. The girls are not pleased. Megan is especially annoyed because Ariel is starting school the next day and she must show her around.
Ariel rides a child's bicycle to school, complete with training wheels. She wears a football helmet. Megan tries to ignore her. When they arrive at school, Ariel crashes into the bike rack and is thrown over it but emerges unhurt. To Megan's surprise, the other students like and accept Ariel, even the snobbish popular girls. Ariel is very smart in all of her classes and has a beautiful singing voice. By the end of the day, her mannerisms and wardrobe are being copied. A few boys even copy her way of crashing into the bike rack and flipping over it. Megan comes to feel that Ariel has taken everything she herself wanted. Ariel doesn't enjoy her popularity and secretly sends a message to Fanul to come and rescue her. She warns him not to tell his father where they are.
Kathy refuses to admit there is anything strange about the Colas and instructs Megan to teach Ariel how to windsurf. But Ariel is too afraid to get into the water. Megan leaves without her but capsizes when she notices Cutter talking to Ariel on the shore. Ariel returns his interest, despite having a boyfriend back home. Megan angrily confronts her and discovers that Ariel is actually very homesick. She also learns that Ariel is as much against the marriage of their parents as she herself is. The girls concoct a plan to break them up.
The plan doesn't work and earns the girls a scolding. But Megan isn't ready to give up. She and Ariel offer to cook dinner for their parents. Trevor has been scared by Megan into pretending to be sick so they won't have to go to their father' house for the weekend. She invites Fred to stay for dinner, thinking that if her mother sees him and Cosmo side by side, she will want to get back together with Fred. But the plan is ruined when Serena Sue unexpectedly drops by. She charms Fred, which was not what Megan had planned. The dinner is ruined because Ariel has mixed it all together in the blender, making a disgusting-looking soup. The adults get rather silly and squirt each other with soda. Megan goes to the bathroom and sees a large bubble, with Ariel's head inside, floating in the sink. She screams and tells the adults that Cosmo and Ariel are aliens. Trevor is the only one who believes her.
Kathy sends Megan to a psychiatrist. He thinks Megan's story of aliens is very common among children who feel threatened by change and urges that the wedding proceed as scheduled.
The ceremony will take place in the Larsons' back yard. Ariel is thrilled when Fanul shows up but horrified to see that his father is with him. The Emperor Svad has come to arrest Cosmo. Fanul is apologetic but reminds Ariel that his father must uphold the law. Serena Sue enters the bedroom where they are talking and Svad turns her into a block of ice. He leaves to find Cosmo and orders Fanul to guard Ariel. Then Megan and Cutter burst into the room. Ariel tells Megan the truth, that they in fact aliens. Megan orders Fanul to release them but he refuses. However, he is obviously attracted to her. Ariel admits that he seemed more appealing as a bubble.
Svad wanders among the guests in his search for Cosmo. He finds him with Trevor. Cosmo sends Trevor off for a game of hide and seek before learning that his fate, along with Ariel's, is to be sealed inside a block of ice forever. Meanwhile, Fanul has changed his mind after the other three teenagers talk to him about what it means to have freedom of choice. They collect blow dryers and turn Svad into a bubble. But he floats above the trees out of range. Trevor comes to the rescue with a leaf blower and Svad is conquered. Fanul is determined to make positive changes on his planet. He promises Megan that he will someday return.
In a voice-over, Megan admits that it is great to have a boyfriend and a best friend. The popular girls' table at school no longer exists, as Ariel and Megan welcome everyone.