Put her down or I'll make you eat your tail. Seriously, I can do it. 
Supergirl (Volume 5) #12 is an issue of the series Supergirl (Volume 5) with a cover date of January, 2007. It was published on December 6, 2006.
Synopsis for "Rock On!"
Nightwing and Captain Boomerang apprehend a couple of purse-snatchers in lower Manhattan as discussing Supergirl. Nightwing is worried about her, thinking she must feel lonely and lacking direction. Captain Boomerang argues she's just behaving like a typical teenager.
Meanwhile, Kara is dancing the night away at a trendy New York club. After the disastrous mission on Kandor II[1] and her failed attempt to have a secret identity,[2] Kara feels uncomfortable trying to live up to everyone else's expectations. Suffering from a mild identity crisis, she's pondering giving up her Supergirl identity for good.
Suddenly, a giant, dinosaur-like monster begins terrorizing the street outside. Kara sees New York's newest hero, Terra, engaging the creature, and as complaining all she wanted was a quiet night, flies out of the club to join the fight.
Both girls try to fight the monster coordinately, but the beast hold them back as ranting about greedy humans digging too deep and invading his underlands. In the meantime he brings a building down. Terra evacuates the endangered bystanders as Supergirl fights on, but the monster grabs her and tells he can feel all of her conflicting emotions: doubt, fear, vulnerability, anger... as projecting an image of Superman's face, he says she doesn't belong there.
Supergirl wonders for one instant if he can be right before unleashing her optic blasts. The monster endures her attack easily and swats her away. Terra engages the monster again, calling him "Empathosaur", as Kara rescues people from a crumbling rooftop. As pondering she's not cut for hero life she can't help but to admiring Terra's spirit and determination.
After taking people to safety, Supergirl confronts the monster, telling him to put Terra down or she'll make him eat his own tail. The Empathosaur ignores Supergirl's warning and tries to get her confused with images of her father's face. Supergirl punches him anyway, but the Empathosaur has the upper hand yet.
Finally, Terra comes up with a plan. The Empathosaur's powers are rooted to the Earth, so Supergirl lifts him as Terra creates a massive crater in the Earth. Supergirl throws him deep into the crevice and Terra seals up the hole. She comments that Empathosaurs thrive in lava, so the creature will come to no harm.
Later, a morose Kara returns home where she has a talk with Captain Boomerang. She doesn't know if she can or wants to be a hero, and her meeting with Terra has only increased her doubts. Owen manages to get her to shake off her blues and the two go out into the night to have some fun.
Appearing in "Rock On!"
Featured Characters:
Supporting Characters:
- Captain Boomerang (Owen Mercer)
- Nightwing (Dick Grayson)
- Terra (Atlee) (First appearance)
Antagonists:
- Empathosaur (Single appearance)
Other Characters:
- Superman (In a vision)
- Power Girl (Cameo)
- Phantom Lady (Mentioned only)
- Zor-El (In a vision)
- Streaky
Locations:
- New York City
- Kandor II (Mentioned only)
- Krypton (Mentioned only)
Items:
Vehicles:
Notes
- This issue is reprinted in the Supergirl: Identity and Supergirl: The Girl of Steel trade paperbacks.
- The events from this issue take place after Supergirl (Volume 5) #10, but before Supergirl (Volume 5) #11.
- This issue introduces a new heroine using the code-name Terra. Previously there have been two distinctive characters to assume this name, both of which were involved with separate incarnations of the Teen Titans. Terra III is featured in her own four-issue limited series published in 2008. She appears next in Terror Titans #1.
- Supergirl became a probationary member of the Outsiders as per Outsiders (Volume 3) #42.
Trivia
- Several of the dancers seen at the night club are dressed as famous DC Comics characters. Among them include: Aquaman, the Atom, Batman, Black Canary, Captain Marvel, Batgirl, Big Barda, Catwoman, the Cheetah, Doctor Mid-Nite, Firestorm, the Flash, Green Arrow, Green Lantern, Guy Gardner, Harley Quinn, Hawkgirl, Hawkman, Lobo, Martian Manhunter, Mary Marvel, Mister Terrific, Nightwing, Phantom Lady, Plastic Man, Poison Ivy, Power Girl, the Riddler, Robin, Starfire, Stargirl, Star-Spangled Kid, Superman, Wonder Girl, Wonder Woman and Zatanna. The party-goer dressed as Big Barda is actually a man using balloons to accentuate his chest.