The Alligator Imagin, based on the story of The Fox and the Crocodile, is an Imagin who enacts his own scheme to change the past.
Kamen Rider Decade
Unlike other Imagin, the Alligator Imagin goes through a multitude of hosts to enact his scheme. He killed a young boy and arrivied in the past on December 30, 2008 by the boy's memory, the Alligator Imagin proceeds to change the future and overpowers Decade and Den-O, taking the latter's DenGasher as his own.
Diend and his KamenRide Card summoned Riotroopers to allow for Den-O and Decade to regroup, and allow for Decade to get the Den-O Cards. With both Kuuga and Den-O, Decade destroys the Alligator Imagin with the Den-O Final Attack Ride.
The Alligator Imagin is one of Dai-Shocker's Great Commanders. When Dai-Shocker and Dai-Zangyack reveal their alliance and fight against the combined Super Sentai and Kamen Rider force, Alligator Imagin, alongside Long of Genjuken, is seen leading a group of Imagins, to fight against the Gekirangers and Kamen Rider Den-O. He was also seen fighting Kamen Rider Agito in the second aerial attack scene.