Digimon: Digital Monsters
Episode 29
S1 E29:
The DigiDestined return to their original camp and then head to Highton View Terrace trying to find the eighth child. There, a battle between Garudamon and Mammothmon helps them all recall how they witnessed a battle four years earlier between a Greymon and a Parrotmon. This leads them to surmise that the eighth child must have also seen the fight.