Felix is a onetime member of the Neutrino Resistance Fighters and Professor Zayton Honeycutt's former assistant. He worked with Honeycutt when the scientist was attempting to perfect the rebels' interdimensional portal technology, but their work was interrupted by an attack by Krang. He assisted Honeycutt in transferring his mind into the SAL robot, and fled the facility. He lost an arm in the attack, but was able to replace it with a robotic arm thanks to Honeycutt's research.
He was reunited with Honeycutt during the Krang War arc, after the END missile was damaged but not destroyed by another attack. After repairing the missile with Honeycutt and Donatello, they launched it and tracked it as it approached its destination.