DigimonWiki:Digivolution References/Adventure:

"Tokyo Digital Crisis" [01]
 * Koromon > Agumon > Greymon
 * Argomon (In-Training) > Argomon (Rookie) > "Argomon (Unknown Form)"

"War Game" [02]
 * "Argomon (Unknown Form)" > Argomon (Ultimate) > Argomon (Mega)
 * Greymon + Garurumon > Omnimon