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troperville

Raven accidentally lets loose on a villain, sparking the concern of her teammates. Beast Boy, still wary of his teammate, makes an insensitive joke that sets her off, and in his attempt to apologize, breaks into her room, along with Cyborg. The two of them happen upon a magic mirror that leads them into a mysterious place, where they find several out-of-character versions of Raven. After discovering that they're in Raven's head, Raven helps force them out by defeating the manifestation of her darkness, in the form of her father.

Tropes:

All Your Powers Combined: Raven beats Trigon by combining all the aspects of her personality.
Battle in the Center of the Mind: Raven vs. Trigon
Butt Monkey / The Chew Toy: This episode sets the trend of Dr. Light being put up against the Teen Titans, only to have his ass handed to him.
Characterization Marches On: Judging by how they were in Go!, it's hard to believe that Beast Boy was so wary of trusting Raven. Though the start of the episode could have changed his opinion.
Chekhov's Gunman: Trigon does not appear in the series proper again until season four, where he is the Big Bad.
Color-Coded for Your Convenience - Raven's alter egos wear cloaks of different colors that match up with the emotion they represent.
Curb-Stomp Battle: Zig-Zagged; Dr. Light was introduced to be subjected to these frequently, but actually holds his own against the Titans. Then Raven comes up to bat.
Dark Is Evil / Dark Is Not Evil: This episode toes the line between these two Aesops. On the one hand, Raven must be careful to keep her dark side in balance, and on the other, she learns not to hide it from the others and from herself.
Genki Girl: Pink Raven.
Hilarious in Hindsight: After the comics version of Dr. Light being unveiled as a rapist, his [Mind] Rape at the hands of Raven becomes an interesting bit of irony.
Hot Blooded: Green Raven.
Journey to the Center of the Mind
Kuudere (This episode really highlights this aspect of Raven's personality)
Literal Split Personality: Plays with this, with Raven having seven alters that represent her emotions.
Mind Rape: What Raven subjects Dr. Light to.
The Other Darrin: This is the only episode where Trigon is voiced by Keith Szarabajka. When he comes back in Season Four, he's voiced by Kevin Michael Richardson.
Shrinking Violet: Gray Raven.
Slasher Smile: Raven displays one while Mind Raping Dr. Light.
What Happened to the Mouse?: The four-eyed Red Raven does not appear again in the TV show, even when Season Four provides many opportunites. She does, however, appear in the tie-in comic.
You Wouldn't Like Me When I'm Angry: Raven warns Dr. Light not to make her angry.