To do this cheat, you must have Sonic Advance 1 or 2 and a Gamecube/GBA link cable.Go to the Chao Garden on Sonic DX, and step on the transporter. Then, turn on the Tiny Chao Garden on Gameboy Advance. Transport the chao you have in GBA to the Sonic DX garden. Then on GBA, go to the chao mini-store by pressing L. You will see a free egg. Buy it, hatch it, then transport it to Sonic DX. Keep on doing this until you have enough Chao.