The episode opens with the Gems investigating a terrible smell from Amethyst's room, which turns out to be a several-year old burrito. As Amethyst takes a bite of it, Steven finds an old framed picture with the older Gems plus his mother in a time period that looks to be several centuries ago. Pearl explains to him that they're much older than any human, but when Steven asks if they'll live forever, she reveals that they don't age but can die from injury. As Amethyst begins to feel the aftereffects of eating expired food, Pearl adds that they can't die from food poisoning either. This prompts Steven to ask them how they fit all their candles on their birthday cakes, only to discover that birthdays are a foreign concept to the Crystal Gems. Aghast, Steven resolves to properly celebrate every single one of their missed birthdays.
Steven attempts to hold a birthday party for each of the Gems in order of Amethyst, Pearl, and Garnet. Not understanding human customs, the standard birthday traditions soar over the Gems' heads, which causes Steven to wonder if he's being too immature. As he leaves and walks through town, he unknowingly begins to age rapidly, with every thought about being too old for various things causing him to grow older several years. By the end of the day, he's become a middle-aged man, and he finally realizes this when he walks into the Big Donut and realizes Lars and Sadie don't recognize him.
When a misunderstanding causes Sadie to chase him out of the store, Steven runs down the beach as the aging process speeds up, until he becomes an elderly man collapsed upon the sand. In this state Lion finds him and brings him back to the other Gems, who are cleaning up the party confections. Upon seeing Steven, they try desperately to revert his age with the birthday traditions he taught them earlier, since his half-human genetics would cause him to die of old age. Unfortunately, each attempt only increases the aging process. When Garnet has a Not So Stoic moment and tries violently shaking him, the Gems begin arguing, which causes Steven to tell them to stop. As he does so however, he reverts from a dying, ancient man back to a teenager state. Pearl realizes that his physical age is connected to his mental state of mind, so the Gems try to snap him out of his depression and make him feel young again. They manage to succeed, and aside from having to sort out the length of his legs, Steven is once again restored to his original age.
We Iris Out over Steven's face as he laughs about the fact that his legs are still adult legs.
- Accidental Pervert: An elderly Steven asks Sadie and Lars "Will you help me into my birthday suit?" Steven meant his king costume that he wears each birthday. He gets chased out of the shop with a stool.
- Adult Fear: You unknowingly convince your child they're "too old" for fun activities, to the point where they figuratively (and literally, in Steven's case) grow up too quickly.
- An Aesop: Even as you're growing older, there's nothing stopping you from doing the "childish" things you love.
- Art Imitates Art: The old painting is an alternate version of Watson and the Shark, which depicts a historical shark attack in Havana, with the Crystal Gems included. Instead of someone preparing to spear the shark Garnet is punching it.The hard part was getting the shark to pose.
- Be Yourself: Pearl tells Steven to think like himself; Sweet, considerate, and only occasionally obnoxious. It's what saves him.
- Birthday Episode: The episode is centered around the concept of birthdays, though it isn't anybody's actual birthday.
- Birthday Hater: Rather than outright hating birthdays, the Crystal Gems merely find all the associated traditions to be incomprehensibly bizarre a rather reasonable reaction in context. Amethyst enjoys them anyway, but Garnet thinks they're too old for them and Pearl is confused and scared by Steven's attempts to be funny.Pearl: I think this is why aging makes humans die!
- Bowdlerise: Steven's still dodgy line that he can't "spend the whole day whackering" was initially pitched as "spend the the whole day whacking it", which the outline supervisor immediately shot down.
- Brick Joke: Onion showed in "Arcade Mania" that he was good at getting lots of tickets at the arcade. We see in this episode that he gets all those tickets by breaking into the machine.
- Comically Missing the Point: Steven hands Amethyst a bat for a pinata, but she thinks Steven was giving her a weapon to fight Pearl with.
- Compressed Hair: Steven looks as if he made his hair rainbow-colored for his clown outfit, but was actually wearing a rainbow wig the same shape. He takes off the wig and his real hair comically decompresses a second after.
- Continuity Nod: Sadie tried to use a footstool to break Steven's bubble in "Bubble Buddies". She threatens to use one again when she's chasing off the elderly Steven after a misunderstanding.
- Darker and Edgier: With Steven nearly dying, the Gems losing their cool in trying to save Steven's life, and the revelation that Steven might NOT be immortal unlike the Gems and could eventually die of old age, this episode is easily darker than any before it.
- Doesn't Know Their Own Birthday: The Gems have never celebrated birthdays before, and have lived so long they don't really know when their birthdays are, so Steven decides to throw a party for all of them right then.
- Double-Meaning Title: "So Many Birthdays" can refer to either the series of birthdays Steven has for the other Gems, or Steven triggering rapid aging on himself.
- Early Installment Weirdness:
- A rancid burrito makes Amethyst throw up, as this was before the writers came up with the idea of her being an Extreme Omnivore who happily eats things like motor oil without consequence. Although it wouldn't be out of character for Amethyst to let herself get sick, just to annoy Pearl.
- During Pearl's birthday, she says she likes pie. Later episodes establish Pearl dislikes eating food in general. One of the writers handwaved her comment to mean she enjoys the process of making it.
- Steven's thoughts and emotions affect his powers throughout the series, but them semi-permanently changing his age never happens or is mentioned again. When he temporarily turns into a baby in a later episode, it's due strain from overusing shapeshifting.
- Empathic Environment: It's sunny at first when Steven has Amethyst's birthday party on the beach, but dark clouds start rolling in during Pearl's ill-fated party. Once Steven starts rapidly growing up, it's overcast and foggy.
- Fan Disservice: Steven aging into an teenager, then an adult, is not made to look glamorous or handsome in any way; he still retains his high voice, and is intentionally made to look awkward, pimples and all as the former.
- Flash Step: When Steven was throwing a party for the Gems because they don't celebrate birthdays, for Pearl's part of the party he intended to trip and fall face-flat on a pie. Pearl caught him mid-fall from a meter or two away to keep him from falling. To respond, Steven just slammed the pie in his face anyway.
- Full-Name Ultimatum: Played with; Steven is angrily referred to by his full name ("Steven Quartz Universe") for the first time to clarify what Steven is being discussed, but what the listeners don't realize is the speaker is Steven.
- Gross-Up Close-Up: The camera focuses in on Steven's face as he become a teenager, causing it to grows hair and pimples.
- Happy Birthday to You!: Steven has his own birthday song, which seems like it was written specifically for the Crystal Gems.It might as well be your birthday.
So why don't we have a party?
Even if your age isn't real,
and your body's an illusion!
- Heroic BSoD: Both Steven and even the Gems go through this rather harshly.
- Steven, upon learning that the Gems are not pleased by his efforts to give them a happy birthday, starts wandering around town depressed and world-weary, thinking that he's too old to enjoy any of the things he likes.
- The Gems' desperate attempt to save Steven from dying results in Pearl being an emotional, teary-eyed wreck and Garnet trying to take drastic measures to save him.
- Hypocritical Humor: Steven realizes he's too old for "kazoo racers" when he gets stuck inside a miniature car. He says it seems undignified now and solemnly walks off, with the car still stuck around his butt.
- I Never Told You My Name: Steven walks into the Big Donut, unaware that he's aged so much Lars and Sadie cannot recognize him. He disturbs both of them by calling Lars by name and talking about "Steven" (angrily confirming that he means the same Steven).
- Incredibly Lame Fun: Pearl starts to admit birthday parties can be fun... because she gets to put things away afterward.
- Instantly Proven Wrong: Steven walks by Onion, wistfully talking about how "innocent" he is right before Onion pries an arcade machine open with a screwdriver to steal the tickets.
- Literal-Minded: Steven makes a joke about Pearl throwing out a stick of butter to see a butterfly. Pearl is hurt at the though that Steven is making up bad things about her.
- Malaproper:Steven: Well, I can't just ignore this tremesty of unjustice!
- Mistaken Age: Until Steven asks the Gems about an old picture, he has assumed they were the age they looked rather than hundreds or thousands of years old.
- Mood Whiplash: The first half of the episode consists of Steven innocently trying to help the Gems have fun and enjoy the Birthday(s) they have missed. The 2nd half involves Steven's character deconstructing into a dying, withered old man with the Gems trying futilely to save his life while trying not to cross the Despair Event Horizon. Since most of their attempts center on trying to make Steven happy, they end up being disturbingly humorous at the same time.
- Never Had a Birthday Party: Amethyst, Garnet, and Pearl never had a birthday party as it's not a Gem custom (and they probably don't know what their birthdays would be, at least not on a modern human calendar), so Steven decides to hold one for them all at once.
- Non-Ironic Clown: Steven dresses up as a clown for Pearl's party, including a Pie in the Face, but to her he definitely comes off as a Monster Clown. Pearl also dresses up as a clown when she thinks it will help save Steven, but her Inelegant Blubbering ensures that wouldn't work.Amethyst: Steven, that is a brave look.
Steven: No, it's funny.
Steven: Uh...oh geez, I'm breaking character.
- No-Sell: Amethyst hits Garnet several times with a bat while blindfolded and swinging at a pinata wildly, but Garnet doesn't flinch.Garnet: (gets hit in the face, slightly annoyed) Higher.
- Not So Stoic: While the Gems are trying to get Steven to revert to his original age before he dies, Garnet picks Steven up and begins shaking him out of desperation. When Amethyst and Pearl stop her, she is seen walking away crying because she doesn't know what to do.Garnet: I thought violence would be the answer.
- Not Quite Back to Normal: By the episode's end, Steven only manages to turn his upper half to his actual age, with the legs still being hairy and adult.Garnet: We'll work on the rest later.
- Oblivious Transformation: Steven doesn't notice his Rapid Aging until Lars and Sadie fail to recognize him. Not even changing his own clothes makes him notice.
- Running Gag: Amethyst accumulates more and more party hats with each birthday party.
- Shameful Shrinking: Steven once shrinks, in both size and age, when he gets embarrassed.Old Steven: (weak) Would you guys, just please...(Gem activates, turning him back into an adult) Control yourselves?! (The Gems stop and pay attention) Ugh, oh no. (transforms into a teen) Oh, I'm sorry, I shouldn't have yelled. (blushes) But I can't stand to see you (ages into adult again) freaking out like this!
- Shapeshifting Excludes Clothing: While Gem shape-shifting usually has Magic Pants, Steven's accidental age changing doesn't alter his clothing his normal shirt is tiny on his adult body and his "Professional Beach Hunk" shirt is too large when he returns to normal.
- Stylistic Self-Parody: Amethyst wears a party hat over her nose, then pokes Pearl's nose with it◊, calling attention to how large and pointy Pearl's nose is.
- Violence Really Is the Answer: Invoked by Garnet, who tries to cure Steven by shaking him, but it fails.I thought violence would be the answer.
- Vomit Discretion Shot: After Amethyst eats a 5-year-old, possibly older, burrito, her vomiting is covered by a Smash to Black.
- Way Past the Expiration Date: A tuna burrito laying around Amethyst's room is unwrapped, spewing out a noxious green cloud. Amethyst explains it's from a restaurant that Steven says closed about half a decade ago. She eats it anyway. Within two minutes, Amethyst turns green all while Pearl is explaining that the Gems can never die of old age... or food poisoning. Then the camera blacks out as she retches.