U9-C4, also referred to as Ceefor and nicknamed "Flat Top" by Colonel Meebur Gascon, was a somewhat timid masculine astromech droid owned by Thongla Jur, a member of the Jedi Order during the Clone Wars. He became a member of D-Squad, a team assembled to steal a Separatist encryption module, and was modified to have a powerful laser cutter installed into his body.
U9-C4 with his enhanced laser cutter extended
Around 20 BBY, U9-C4 was chosen to be a member of D-Squad and was placed under the command of Colonel Meebur Gascon, who showed little respect to the droids and only regarded them as property. Before their mission, the droids visited the Parwan doctor Gubacher to receive upgrades for their mission aboard the dreadnought. Ceefor was fitted with a laser cutter that, while able to cut through nearly any material, required him to be in a locked position due to the laser's powerful recoil. After the squad successfully boarded the dreadnought, Gascon tasked Ceefor with using his laser to cause a temporary power loss in the comm-vault's power supply, but the droid forgot to secure himself beforehand and the recoil knocked him into the wall behind him, though he did succeed in his task. Later, after M5-BZ short-circuited attempting to open the vault door, Gascon rode on top of Ceefor's head for the rest of the mission.
After successfully obtaining the encryption module, D-Squad encountered a swarm of ice comets and were forced to crash land on the planet Abafar, eventually coming across the settlement of Pons Ora. After receiving help from the amnesiac clone trooper "Gregor," Ceefor and the other droids stole a shuttle from a nearby landing zone and departed the planet.
U9-C4 was modified with a powerful laser cutter.
Ceefor and the squad later made it aboard the Renown that was in orbit with the encryption module only to find that the ship had been taken over by the Separatists, who planned on using it (along with the large supply of rhydonium they had on board) to blow up a Republic space station in the Carida system during a Republic strategy conference. Luckily, D-Squad was able to foil the plan and afterwards, Ceefor and the rest of the droids were assigned to the same platoon as Gascon.