Agumon is Tai's Rookie digimon companion.
Koromon is the In-Training form and
Greymon
is the Champion form.
Tai has the crest of courage and this allows his
digimon companion to evolve to Metal Greymon - the Ultimate level and then into WarGreymon.
Agumon is made with a toilet paper tube, a
printer, a piece of paper, some crayons, scissors and glue. I always prefer to use a
heavy paper (like construction paper), but it isn't necessary.