A magical mishap caused the Mane 6, Spike, Tirek, Chrysalis and Cozy Glow to be teleported to the DCAU.

The Deadly Alliance find themselves at the Hall of Doom, surprising the villains. Tirek offers an alliance between them. Gorilla Grodd isn't interested and tells Tala to destroy them with her magic. But Tirek absorbs her magic, making him stronger, having never tasted this kind of magic before, which nearly drained Tala. Intrigued, Grodd reconsiders.

Some of the villains don't take Cozy Glow seriously, for obvious reasons. This makes her angry, thinking just because she looks all "cute and cuddly" that she's supposed to be nice, kind, and friendly. She screams at them that she's not friendly, all she cares about is power and do whatever she wants and force people or pony to do whatever she asks for or else.

After a moment of stunned silence, Bizarro suddenly laughs and says "Aww, cute little baby horsey is just like Baby Doll!"

With all that out of the way, the two groups begin their plan.

Lex Luthor probably tries to convince the three to overthrow Grodd so he could lead the Legion.