The Bad Batch, officially known as Clone Force 99 and designated as Experimental Unit Clone Force 99, was a Clone Commando Special Forces Squad that was active during the Clone Wars. The squad initially consisted of four Clone Commandos that were designed with genetic mutations and led by Clone Sergeant CT-9901 'Hunter', a Clone with enhanced sensory abilities. Other members of the squad included CT-9904 'Crosshair', a Clone with keen eyesight and marksmanship that allowed him to excel in long-distance firefights; CT-9902 'Wrecker', a reckless Clone with an enhanced muscular form, and CT-9903 'Tech', a Clone with enhanced mental capacity and intelligence.
Following the crucial Battle of Anaxes, Advanced Recon Commando Clone Corporal CT-1409 'Echo' joined the unit because of his cybernetic enhancements forcibly installed in him by the Techno Union during his capture and containment since the Battle of Lola Sayu and his severe injuries suffered during the Citadel Rescue.
Most of the members' mutations and the ordeal Echo suffered prior to joining caused their inhibitor chips to have less effect, meaning Clone Force 99 was able to disobey Order 66, at least at first appearance, while they were fighting in the Conquest of Kaller, and Hunter helped Jedi Padawan Caleb Dume escape the 'Reg' Clones by lying about his death. However, it was later discovered that unlike the rest of the team, Crosshair was affected by his chip, attempting to kill Dume during the incident.
In the aftermath, as the Galactic Republic became the Galactic Empire, the Bad Batch's loyalty was questioned by Admiral Wilhuff Tarkin. He sent them on a mission to eliminate a group of insurgents in the Onderon Sector, but as the squad found out, that was not what was happening. After the squad disobeyed orders to kill civilians and former Republic fighters, all of the squad's members-save Crosshair-deserted from the Empire, taking with them Omega, a young experimental female Clone they met on Kamino.
Now fugitives from the Empire, they eventually came to work as mercenaries for the information broker Ciddarin Scaleback, more commonly called 'Cid', in the early Imperial Era.