The episode starts off with Todd, Judy, and Dustin singing Happy Birthday to Reggie. Reggie blows out the candles on her birthday cake, Judy takes out her presents afterward. After accepting Todd’s and Dustin’s gifts, she opens up one from Judy herself, only to be caught off guard by the frilly blouse inside. Judy doesn’t notice Reggie’s uncomfortableness and comments that she should wear something a little bit nicer for once. Reggie is further disappointed after opening the rest of her gifts, turning out to be other ‘girly’ things like a hairbrush and deodorant among other things. Judy hands Reggie her last present, Reggie getting excited as she thinks it’s Corporate Battle Snake Melissa. She is immediately embarrassed upon finding out it's a pink bra. In shame, Reggie declares that the party is over, and Dustin leaves for his room. Judy gives Reggie a talking-to, saying that she’s growing up and that she has to make room for her to mature.
Judy, Dustin and Kathy are in the garage, preparing for the upcoming garage sale. Judy digs in through a cardboard box full of Reggie’s old childhood toys, planning to sell them. She places a label that reads ‘free’ onto Brown Roger, before Reggie and Todd enter the room and interfere. Reggie removes the label, distraught over Judy wanting to sell her childhood toys. Judy gives Reggie one more day to go through her toys, keeping what she absolutely can’t live without. Todd insists helping Reggie clearing out her things, and the two take the box - along with her mom’s label maker - to her room. After reminiscing old childhood memories with Todd, Reggie gets the idea to take her toys to Endless Island so she can keep them forever.
Once on Endless, the number on Twelve’s chestplate changes from 11 to 12, Twelve unenthusiastic about the change. All the inhabitants greet Twelve and Todd as soon as they arrive, wishing the former a happy birthday. Finding out that Twelve accidentally brought the label maker to Endless, Todd insists that she chuck it. A crowd gathers around and using her super strength, Twelve chucks the label maker, immediately feeling better about the whole ordeal. It lands in a volcano, Dr. Champion drying off his clothes using the lava nearby. The lava bubbles in the same spot the label maker fell in, forming a gigantic label maker monster. Dr. Champion runs away in fear.
Back in Bethune, Judy and Kathy continue to set up for the garage sale. Judy comments on how she doesn’t understand why Reggie seems to not want to grow up unlike she did when she was her age. On Endless, Twelve and Todd wonder where they should hide Twelve’s stuff. Colin appears, suggesting that they should bury them in the sand. Not wanting Brown Roger to get covered with sand, Twelve keeps Brown Roger tied to her back and the two bury the rest of the things. Pretty Please, Tater Tot and Beth arrive, telling Twelve that they wrote a birthday song for her, leading the two away from the pile of buried items. Colin notices strange beams of light coming out of the pit.
Twelve and Todd try to endure the trio’s performance, before being interrupted by a now-alive Flaps flying around them. Twelve and Todd, in disbelief, follow Flaps and discover the pile has been unburied with all the things missing, dicovering they also happen to be alive soon after. Twelve buries Brown Roger in the sand, and he comes to life as well. The ground suddenly starts rumbling and the label maker monster reveals itself to the denizens of Endless. Twelve is welcoming at first, but the label maker monster knocks her to the ground. With the help of their new friends, Twelve and Todd defeat the label maker and it oddly explodes. Soon after, the two leave Endless and return back to Bethune.
Reggie knocks on Dustin’s door, the latter being annoyed by her presence, Reggie shows him Mr. Ratty, saying that she sneaked him out of the garage sale and that she thought he could have him. Pretending to not care, Dustin shrugs it off, but pets Mr. Ratty and smiles to himself once Reggie is gone. In her room, Reggie draws a picture of Brown Roger in her journal, tears the page off and pins it to the wall beside her bed. Judy arrives outside her door, asking what she decided to keep. Reggie lies, saying that she decided to get rid of it. Feeling proud of her daughter for being a bit more mature (which Reggie denies she isn’t), she wishes Reggie a good night before leaving. The episode ends with Reggie going to sleep and the camera panning to numerous drawings of all her new friends on Endless on the floor.
- The following list isn't in chronological order of the appearance in the episode.
- This is the longest episode of the first season.
- Reggie mentioned, "It's more beautiful, every time I see it", just like the last time she said it.
- This is the first episode where it is someone's birthday. The second episode being, "Todd Forever" where it is Todd's birthday.
- Click here to view image gallery of Birthday Forever.