Piper and Moose follow Natalie around outside until she wants to come in.
When they get home, their mom is making a cake, and invites Piper to the birthday party. Moose is surprised—no one ever gets invited.
Moose finds himself in a bad mood, so he locks himself in his room until dinnertime. Piper comes banging on the door, and his parents give him a hard time, saying that he needs to be polite for his "girlfriend." Poor Moose.
Moose is irritated by these girlfriend comments, and it only gets worse when Natalie keeps repeating Theresa's name, so their mom asks Moose to invite Theresa—his "other girlfriend".
Theresa comes over and they make it halfway through the birthday song before Natalie interrupts: Annie's not there.
Moose's mom looks slightly annoyed, but allows them to go get Annie. Before long, it's a full-fledged birthday party.
The kids are all really nice and friendly to Natalie, which shows Mom how well everyone's been taking care of her.
After the presents are opened, it's time for Moose to walk everyone home. Of course, Piper is the last to be dropped off.
When they get to the door, Piper asks how old Natalie really is. When Moose tells her she's sixteen, Piper nods and says that "we" thought so. Moose doesn't really like that she used the word we. We feel you, Moose.