R2-D2's battle droid squadron/Legends

"R2, look out! Behind you! You're being followed by battle droids!"

- C-3PO, upon seeing the squad.

The squadron consisited of a trio of battle droids that had been captured by the Republic and reprogrammed by R2-D2 to follow his orders.

History
During the Clone Wars, at least three OOM pilot battle droids, were captured and reprogrammed for use by the Republic. The Republic put the astromech droid R2 in charge of this small squadron. The squad's only known mission was the rescue of Jedi Council member Even Piell, during which the droids piloted a shuttle, carrying the rescue team, to the Citadel. They landed somewhere in the out-lands and deployed the team; later, they were ordered to pilot the shuttle to the Citadel's landing platform. There, the team was forced to abandon the shuttle to avoid suspicion from the Confederacy of Independent Systems' forces.

While in the Citadel, they saved Obi-Wan Kenobi and his team. Pretending to be Confederate battle droids, the squad escorted the "captured" Obi-Wan to the landing bay. It was during that time that the Confederacy found out that the droids were reprogrammed and were serving the Republic, forcing the group to engage Separatist droids. One of the squad's members was shot but not destroyed in the ensuing battle. After the demise of ARC Trooper Echo, the rescue team was forced to retreat and hide in a cave. After contacting the Jedi Council for reinforcements, R2-D2's squad, along with the rescue team, went on to find a way to get to the extraction point, during which the unit was ordered to hold off the pursuing Confederate forces, which resulted in its destruction.

Destroyed
"All for one and one for&hellip; ahhh!"

- One of the battle droids before being destroyed

All three droids were destroyed when R2-D2 ordered his squad to hold off the Separatists long enough so that he and his comrades could climb down a cliff. The battle droids exclaimed their honor of serving under him before the group left. They made a final stand against the enemy forces and were ripped limb from limb and destroyed by crab droids.

Behind the scenes
There may be another error here. In the episodes The Citadel and Counterattack, there were three droids under R2's command among which one was later destroyed. But in Citadel Rescue, there were still three battle droids accompanying the team despite the one being destroyed in the previous episode.