Here's how Brian and Sunset Shimmer join the fight in Revenge of the Red Diesel.
[we sideswipe back to Kamino where we see the battle is still raging on, and we aslo see that Skystar has engaged Novo]
Princess Skystar: Mother, stop! It's me! Skystar, your daughter!
Queen Novo (darker voice): Then she can be my little inquisitor!
Queen Novo (darker voice): Deal with it! [force pushes her back]
[they firously clash sabers, as the other continues battling the clones]
[Soon, Brian, Sunset, and K2 arrive]
Sunset Shimmer: [hands K-2 a blaster pistol] You'll need this.
K-2SO: My goodness! Shut me down!
[then Hiro's shuttle lands]
Princess Luna: Surprise!
Brian: Luna, Hiro!
Hiro: You really think we wouldn't join in this battle. In a situation like this, it involves every single member of the Republic.
Princess Luna: Now, let's destroy these clones!
Brian: Right! [ignites his Lightsaber]
[They charge strait forward as it cuts back to Coruscant]