Don't worry, Steven, it doesn't matter to me what age it seems like you are, I wanna hang out with you no matter what. Your dad still has his carwash and the Gems have to do Gem stuff so I'll watch you when they're not around. I can come see you after I'm done training with Pearl too. Doesn't that sound fun?
The Gems are setting up a party for Steven outside of the barn, inflating balloons and fitting them with ribbons. Steven is concerned if it's alright if they stop working on the drill for this occasion, and Pearl says that Peridot should keep things in check. Amethyst teases a passing Peridot about the party, failing to amuse her. Garnet reasons that they should celebrate Steven's progress and that he has grown and learned a lot the past year. Connie arrives in Greg's van and celebrates Steven's birthday. Connie explains that it was hard to convince her parents to let her stay in Steven's barn for the weekend, refusing to let her go without an array of safety equipment, including a defibrillator.
Greg runs up to hug Steven and celebrate his birthday. He is astonished that Steven grew up so fast, seemingly from a baby just yesterday to being fourteen now. Connie is surprised to learn Steven's age and that he's older than her, being only twelve and three quarters. Greg shows Connie a photo album of Steven's birthdays, showing that he grew normally between the ages of one and eight, but from that point his growth had stunted. After excusing Steven to talk to Greg in the van privately, Connie expresses concern for Steven's growth. Greg isn't sure himself why this is happening and how it'll resolve, considering Gems don't age at all, but since Steven is half human as well his properties are unpredictable. Steven overhears the conversation as Greg finishes by saying that they should wait and see how Steven grows.
At the entrance to the barn, Steven tries to hang a birthday banner but couldn't do it because the mouth is too high. Amethyst approaches him and advises him that if he could stretch his limbs, he would be able to hang the banner. Greg comes up to Steven and gives him his birthday crown and cape, putting him in the barn and closing it to give Steven a surprise later. In the barn, Steven contemplates on whether or not he should shapeshift himself so that he looks older. Everyone outside yells for Steven to open the door for the surprise and are immediately shocked at Steven's sudden change of physique. Garnet compliments his appearance but Connie expresses her disbelief and skepticism over his sudden "growth spurt". Later, Connie gives Steven a gift box, revealing it to be a pink shirt. He tries it on but it doesn't fit perfectly well. Pearl, Amethyst, Steven, and Connie play badminton, and Amethyst shoots the racket far away into a tree. Connie tries to retrieve it but Steven pulls down the branch using his height. After Connie leaves, his arm shapeshifts into its original form, but Steven forces it back.
In the evening, Steven, Connie and the Gems are dancing. Garnet changes the song to fit the mood for Steven and Connie to dance alone together. Connie makes joking remarks about Steven's age and new height, and tells him that it's funny in a good way that she has to literally look up to him. Steven becomes too uneasy and nervous, excusing himself to take a break. He runs behind the barn out of sight to shapeshift back into his original form. Amethyst and Greg witness Steven's shapeshifting and are in shock. Steven shifts back as they both question him. He explains that he needs to stay this way so he can keep a mature appearance towards Connie. Amethyst warns him that he could greatly harm himself if he keeps stretching his form, but Steven dismisses her warning under the excuse that he's half human so they know nothing about his possible properties. Connie and Steven sit under the stars, pointing towards self-made constellations. Connie expresses her happiness in the prospect of growing up with Steven, which makes him shapeshift into an infant form and cries.
Connie shows Steven to Greg and the Gems as they all share the same feeling of shock. Garnet tries to calm him down but he keeps crying. Greg takes responsibility for his safekeeping and care as a child, as he is the only human parent and takes Steven for a short drive with Connie to calm Steven from crying. On the road, Greg is surprised that driving didn't calm Steven down as it did before. Greg wants to drop off Connie to her house, but she insists on staying, offering her assistance as the Gems always go on missions and Greg is usually busy at the car wash. She wants to stay by Steven's side no matter what happens, which seems to calm him down. The following morning, Connie wakes up to see only Steven's shirt on the table, assuming Steven has reverted into a zygote, but goes outside and sees Steven is back to his original form. He apologizes to her, explaining that he wanted to look and feel older for Connie, but she simply tells him that it's perfectly fine if Steven stays the way he is. She notices that Steven is starting to grow facial hair. She shows Greg and the Gems his new discovery and impressing them, as the iris star closes on Connie's face, happy and relieved.
- For Steven's birthday, the Gems made him a Cookie Cat-shaped chocolate and vanilla birthday cake, with a red "1" candle and a blue "4" candle resembling how Garnet was going to tell Steven how Ruby and Sapphire met.
- Greg's first meeting with the Crystal Gems occurred when he was 22.
- Greg's photo album shows that Steven hasn't aged properly since he was 8.
- However, as of Steven growing his first facial hair, it shows he does actually age, albeit at a slower pace.
- The album Greg pulled out of the box had the same album cover of Estelle's Shine with the artist instead being named "Stella", momentarily breaking the fourth wall.
- One of the posters inside Greg's van is titled "Pet Rock" with what appears to be a dog playing a guitar that bears a striking resemblance to K.K. Slider from the Animal Crossing franchise.
- The Durian Juice from "An Indirect Kiss" is seen again.
- Steven's Birthday Suit from "So Many Birthdays" is seen again.
- Steven is shown to use his age manipulation powers again. Once again, it was a disaster as in "So Many Birthdays". Except it works in reverse this time, so instead of aging him so old he nearly dies, it ages him backwards until he is an infant. Also, he has shown to have more control over his shape-shifting powers.
- When baby Steven, Connie and Greg are in the van, the song "Let Me Drive My Van (into Your Heart)" can be heard, as Steven started to like it in "Laser Light Cannon".
- Greg and Connie do their "human beings" high five as they did in "We Need to Talk".
- When Connie is sitting next to Steven on the picnic blanket, her head is bigger than normal.
View the episode's transcript here.