Derek is the AustralianDigiDestined encounter by Cody and Joe. He have digimon partner, Crabmon.
Digimon Adventure 02
Shortly after Hogan, Cody, Joe, and their partners destroy a Control Spire on the coast of Australia, they hear Derek calling from a surfboard for help as he flees with Crabmo from a Gesomon, Shellmon, and Ebidramon. When he makes it to shore, he introduces himself to Joe, Cody, and Hogan. Joe and Cody help deal with the Digimon by having Armadillomon, Ikkakumon, and Crabmon threaten to cook them and turn them into "Digimon Seafood". The threats work and Gesomon, Shellmon and Ebidramon flee. Ikkakumon, Armadillomon and Crabmon chase them towards the Great Barrier Reef, where another Control Spire is located, while Joe, Cody, Derek, and Hogan follow behind them on a small boat.
Once they see the Control Spire, they stop their pursuit of Gesomon, Shellmon and Ebidramon and focus on destroying the Control Spire. A Scorpiomon tries to stop them. Zudomon and Submarimon struggle to defeat the Digimon, so Derek digivolves Crabmon into Coelamon, who turns the tide of the battle. They defeat the Scorpiomon and destroy the Control Spire, just as other Australian DigiDestined arrive with the Digimon they had found.
After the crisis is over and everyone has returned home, Derek celebrates Christmas with Crabmon by eating pizza and giving Crabmon seafood.
As the DigiDestined battle MaloMyotismon, Derek raises his Digivice in Sydney and sends his power to Crabmon. He is then transported to the Digital World.