After hearing of Connie speak of school and summer vacation, Steven gets Pearl to set up a school for him since he's never been. He doesn't know what he needs to do afterward, but when he mentions wanting to learn, Pearl conjures a mirror that they found at the galaxy warp that can show the viewer anything from Gem history and culture. But when Pearl tries to activate it, nothing happens. She decides it's broken, and declares that's the end of school. Steven figures that even without the magic, it's still good as a mirror. He runs off with it in his hand, excited about summer vacation.
Steven cavorts backward into Beach City with the mirror and runs into Lars, who snaps at him for not watching where he's going. After a brief conversation with Lars and Sadie, Steven takes off, still walking backward. He doesn't see Mayor Dewey driving down the boardwalk toward him, but the mirror does, and warns him:
He realizes the mirror is not just what it seems, and asks it what else it can do. It repeats Steven's raspberry noises all through the mayor's speech, amusing Steven and the crowd. Steven lies on the beach to talk to the mirror...all afternoon until dusk. It shows several other reflections to tell him:
When he excitedly tells the mirror he wants to show the Gems, it uses a reflection of Steven and tells him "Nooooo!" in no uncertain terms. Steven insists it will be okay, even as the mirror repeats "No!" over and over, finally going silent when Steven tries to tell the Gems about the mirror. It plays possum but Steven tries to coax it into revealing itself. When the Gems realize it's talking, they react with alarm and distress because it shouldn't be able to do that. Steven tries to get the mirror to show it can talk to him, but it tells him that it only wants to interact with him. When the mirror sees the Gems approaching, it cries "No!" again, obviously upset. Garnet wants to take the mirror. Amethyst wants to bubble it. Steven tells them to back off because the mirror is screaming, and he obviously feels bad it's so upset. He attempts to slap Garnet's hand away when she reaches for the mirror. But he hits her face and knocks her glasses off, enraging her. Steven runs off with the mirror, calling back an apology for striking Garnet. The Gems then chase after him.
When he gets to the beach, Steven asks the mirror why it's so upset and freaked out. It responds by saying "Away from home. Let Me Out!". Steven, ever compassionate, asks what he must do. The mirror gives him a silhouette animated image of himself removing the cracked gem off the back. Steven does so, and the teardrop shaped gem forms into a blue person in a blue gown. She introduces herself as Lapis Lazuli and enthusiastically thanks Steven for talking to her and helping her.
The Gems arrive at the beach, ready to fight. Steven gets between the Gems and Lapis, not wanting to see the Gems fight, since he recognizes the new person as a Gem. Lapis, on the other hand, very much wants to fight — she conjures a giant arm out of the seawater and raises it to attack. She accuses Garnet, Amethyst and Pearl of knowing she was in there and not doing anything to help her, or even trying to find out who she once was. She tells Steven to come with her, and when he hesitates, she leaves him with a warning to not trust the Gems, and departs.
Pearl confirms Steven's inquiry that Lapis Lazuli was indeed another gem. Garnet declares Steven grounded as the scene focuses on a star in the distance, and irises out.
- And I Must Scream: Lapis spent centuries bound inside a magical mirror. She could speak only when spoken to...Except that the Gems did not speak to her, ever. The revelation about the Gems knowing that there was somebody trapped in there and doing nothing about it was quite a "What the Hell, Hero?" moment.Steven: What's it like being a mirror?
Lapis (in mirror): (Playing back Steven's voice) You work!
- Antagonist Title: Mirror Gem naturally refers to Lapis, who was sealed in the mirror.
- Blatant Lies: Garnet says the mirror can't want anything because it's just a tool as it cries out not to be taken away.
- Cliffhanger: This episode leads straight to the next one.
- Come with Me If You Want to Live: Lapis to Steven as she says the Crystal Gems can't be trusted.
- Continuity Nod:
- Connie can't hang out with Steven because she has tennis practice.
- Mayor Dewey recognizes Steven as the "car wash kid", from when Steven and Greg were washing his truck.
- Death Glare: Garnet gives a terrifying three-eyed stare to Steven after he accidentally hits her face.
- Exact Words: Pearl does tell Steven that she's showing him a Gem-powered mirror.
- Geometric Magic: As Steven pries Lapis' gem out of the back of the mirror, Lapis draws water from the ocean into an elaborate geometric circle around him, possibly to help him manage the feat.
- Hearing Voices: The Gems think this is the case with Steven and the mirror, until he coaxes it into talking.
- Iris Out: The star-shaped iris closes over a distant star above the ocean. At the instant it's swallowed, it shows a diamond-shaped shine.
- Lampshaded Double Entendre: Courtesy of Lars.Lars: All those out-of-town summer babes, travelling away from home without their boyfriends, if you know what I mean...
Steven: (beat) Nope!
- Magic Mirror: Pearl says the mirror is supposed to record and replay anything it has ever seen, but assumes it to be damaged when it won't respond. Steven discovers that the mirror is actually sentient.
- Making a Splash: Lapis has water powers.
- Mood Whiplash: The first half is with Steven having humorous fun with the mirror, until the second half deals with the dramatic appearance of Lapis.
- My Name Is Inigo Montoya: Lapis announces her name as she curbstomps the Crystal Gems."I'm Lapis Lazuli, and you can't keep me trapped here anymore!"
- New Content Countdown Clock: Since "Mirror Gem" and "Ocean Gem" were a special two-episode event, they put the countdown clock up for it.
- Not in Front of the Kid: Lars seemingly stops himself from swearing angrily at Steven because Sadie was staring at him with a concerned look on her face.
- Not So Stoic: Steven accidentally hits Garnet in the face to protect a magic mirror and she seems angrier at being hit than with the fact he refused to hand over the mirror.
- Oh, Crap!:
- The Crystal Gems are horrified to see the mirror gain sentience and desperately try to get it away from Steven.
- Steven, upon realizing he hit Garnet and knocked her shades off.
- O.O.C. Is Serious Business: The Gems completely change in attitude when they realize the mirror is sentient. It's actually pretty jarring, especially with Garnet, who at this point in the series has never gotten mad at Steven for his shenanigans. However when Steven accidentally hits her before she could grab the mirror, seeing Garnet angry at him, WITHOUT her sunglasses on, is both startling and scary.Garnet: That little boy is in BIG trouble!
- Parenthetical Swearing: After Steven bumps into Lars, the way Lars says "Watch where you're going, you little...Steven" makes it sound like he had a very different word in mind. Amusingly, Lapis uses this audio clip every time she wants to say Steven's name.
- Poor Communication Kills: Lapis probably wouldn't have been released had the Gems been upfront with Steven about the true nature of the mirror. Instead, they tried to take it back without discussion, and Steven sided with the obviously frightened mirror.
- Quote Mine: Lapis uses bits of recorded audio she's heard to communicate with Steven.
- Sealed Good in a Can: Or Sealed Evil in a Can. The mirror is revealed to hold a Gem named Lapis Lazuli. And she desperately wants out.
- Shouldn't We Be in School Right Now?: Neither Steven nor the Crystal Gems have ever heard of school.
- Super OCD: Pearl takes the disorganized school supplies and stacks them into a symmetrical tower. Amethyst has some fun at her expense by constantly putting stuff on it, causing Pearl to stab the items and complain about the lack of symmetry.
- There Is Another: The Crystal Gems were thought to be the Last of Their Kind until this episode introduced another one.
- Toilet Humor: When Mayor Dewey gives a speech about summer to Beach City, he unintentionally provides bait for several fart jokes. The mirror apparently found this joke so funny she kept repeating it for hours.Mayor Dewey: A warm summer breeze wafts through the air...
MD: We all look forward to the sounds of the summer season...
Mirror: (as Steven) pfrrrrrrt
MD: The smells of the busy boardwalk, (pfrrrrrrt) the hot, wet, ocean wind, (pfrrrrrrt) the time to take that pressure that's built up all year and just let it out! (pfrrrrrrt)
- Too Important to Walk: Mayor Dewey seems to think this of himself, which is why he's driving down the boardwalk in his campaign truck.Steven: Why were you driving down the boardwalk?
Mayor Dewey: I'm the mayor, I'm not gonna walk anywhere
- Wham Episode: The mirror turns out to be an imprisoned Gem named Lapis Lazuli, who is not associated with the Crystal Gems and in fact hates them. Before this, the Crystal Gems were assumed to be the Last of Their Kind.
- What the Hell, Hero?: Lapis calls the Crystal Gems out on knowing she was trapped in the mirror and not making any attempt to help her.You...you three knew I was in there and you didn't do anything... Did you even wonder who I used to be? I am Lapis Lazuli, and you can't keep me trapped here anymore!
- You Are Grounded: Steven is grounded at the end of the episode.