THE BIRTH OF GREYMON (Episode 2) 

While running to escape from the evil Kuwagamon, the kids are knocked off a cliff.  As they plunge to a river far below, Gomamon has the fish in the river break their fall, saving everyone. 
On a beach near the river, the kids discover a series of phone booths, but the phones inside just spout gibberish.  Joe keeps trying to get through to someone, while Tai and Agumon pig out on the emergency food.  

Suddenly the kids are attacked by Shellmon, an evil Digimon.  The digimon are so weak from hunger they can't fight.  But Agumon (who ate the emergency food) digivolves to Greymon and defeats Shellmon with his Nova Blast.  

Soon after everyone recovers, they give almost all their food to the Digimon to keep them strong.  The kids and their Digimon friends decide to search for whoever built the phone booths.