Cullen Calix (Japanese: ペニシリーナ Penicillina) is a supporting character who appeared in Mewtwo Returns.
Cullen is a Pokémon naturalist who specializes in medicine. He made his way to Mount Quena to conduct research on Clarity Lake's environment and its alleged medicinal properties. He also escorted Domino, a Pokémon Institute employee, to the area and was unaware of her affiliations with Team Rocket.
Both he and Luna Carson helped Ash, his friends, and Mewtwo fight against Team Rocket. After seeing the baby Nidoqueen and Rhyhorn amongst the clone Pokémon, alongside Luna's deep attachment to the area, Cullen developed a deeper respect for Clarity Lake. He decided to abandon his cutting-edge research on Lake Clarity's healing properties, in fear of jeopardizing the natural environment. He did take a sample of the spring and hoped to develop a synthetic version instead. Despite his personal resolution, Mewtwo wiped Cullen's memory of the day's events, fearing his ambitions were still a threat.
After the incident, he decided to stay with Luna, seeing that the pair have a lot in common besides research.