"Space Invader" is the twelfth episode of The Loud House.
Everyone is getting ready for bed, and Lincoln is happy because he's the only one in the family who doesn't have to share a bedroom (even if his room is just a converted linen closet), since his parents and all of his sisters share bedrooms. Even though he's got the smallest room, Lincoln's still happy that he doesn't have to share it with anyone. However, just before he can prepare himself to bask in a glorious solo slumber, his sisters Lynn and Lucy start having a quarrel over how they can't stand each other's lifestyles and habits. Lucy can't stand Lynn's energetic and sporty demeanor, while Lynn can't stand Lucy's depressing and negative vibes. The other sisters don't want to get involved in this and just decide to pretend they never saw that. Lynn decides that she doesn't want to spend the night with her roommate. She knocks on Lincoln's door and asks if she can spend the night in his room. Lincoln doesn't feel too comfortable about it at first, but after Lynn makes puppy dog eyes he eventually gives in and lets her stay just for tonight. Lynn is happy to be bunking with Lincoln.
As soon as Lynn enters, Lincoln tries to tell her to not touch his stuff, but she takes his toothbrush, and uses it as her own. Afterwards, she plays with his toys which he doesn't like. Later, Lynn notices Lincoln's room has a "lack of balls" and dumps her own sports balls all over the floor. Lincoln suggests that they go to bed, but Lynn's not tired. She wants to play Lucha Libre, then puts a mask over Lincoln's face. Lynn pins Lincoln down for the count and wins the match. After that, they decide to get some sleep. During the night, Lynn's bouncing a tennis ball across the room. Lincoln tells her to stop, but she does it to help her get to sleep. Later, Lynn lets out a big fart, and smothers Lincoln under the covers in what she refers to as a "Dutch oven". She even snores so loud and drools so much, that Lincoln can't get any sleep, so he goes to sleep in the bathroom where is peace and silence.
The next morning, Lori is getting ready to take a shower to start her day but notices that Lincoln is in the shower and asks him angrily what he's doing. Lincoln then answers that he's getting his room back. Luan notices Lincoln walking and asks him wet's up while laughing. Lynn stretches saying she slept well and comments Lincoln looks terrible. Since the agreement was that Lynn could only stay in his room for one night has already passed, Lincoln kicks her out and takes his room back. But Lynn and Lucy are still not speaking to each other and Lynn decides that she'll spend another night in Lincoln's room, much to his dismay. Lincoln begs Lucy to make up with Lynn, but Lucy refuses to by saying she'd rather wear pink, something a goth like her would never do. On the way to school, Lincoln explains to Clyde what happened, but can't just kick her out given the circumstances beyond his control. Just then, he gets an idea that will surely drive Lynn out. He turns around back to his house to set it up, but Clyde reminds them they still have to go to school, to which he turns around thanks to the reminder.
Lincoln's plan that night is to fight fire with fire so Lynn will think he's the worst roommate ever. He first tries dresses up as a goth and reading Lynn a depressing poem to mimic Lucy's lifestyle in hopes that she thinks that he's now following in Lucy's footsteps and doesn't want to hang with someone who is like her gloomy sister, but she thinks he's just impersonating her for fun and is impressed with him doing it spot-on so that backfires. Next, he tries fighting dirty in a Lucha Libre rematch only for Lynn to commend him for his sneaky tactics. Finally, he gives her a taste of her own "Dutch oven", and it seems like she's finally had enough and is going back to her room with Lucy. Lincoln has his space back, but Lynn returns and brings all her stuff in and declares Lincoln the best roommate ever and decides to move into his room as a permanent resident.
The next morning, after another shower awakening, Lincoln notices that Lucy and Lynn actually do miss each other as they are holding onto some of the trinkets that they gave each other, while denying it to Lincoln.
He's even more tired while walking to school and at his wit's end about this whole Lynn issue. He'll never get her out of his room and he'll be stuck as her roommate forever unless he can find some way to get her and Lucy to make up. He knows that they miss each other, but they just don't want to admit it. Clyde suggests having a nice candlelit dinner for two while imagining himself and Lori having one due to his undying and unrequited love for her. Lincoln decides to give it a try...right after school.
That night, Lincoln slips some invitations to Lucy and Lynn to meet in their room for dinner. As they meet, the two of them, instead of preparing to apologize, are awaiting the other to do so, thinking it's the other's fault their little squabble started. They have themselves a little feud and Lincoln admits that he set up the whole dinner so that they could make up and Lynn could move out of his room and back into Lucy's. They then see what he tried to do and have themselves a little food fight to show that they have made up. However, the mess they made with the fight seems to have covered up both of their beds and they ask Lincoln for a favor.
So Lincoln is finally happy to have his room back, but due to the mess from the food fight he does have to share it for one more night. And it's not just Lynn this time, but Lucy as well. Lincoln puts on his Lucha Libre mask to block out Lynn and Lucy's snoring and bids the viewers, "Buenas noches".