Archived KimimaruTCRF video from YouTube. Original description mostly intact:

This showcases how Egg Animals can damage bosses if hacked into boss battles. They do quite a lot of damage too, which trivializes many bosses.

You can find more information on TCRF, including codes to put Cipher in boss battles, here: https://tcrf.net/Billy_Hatcher_and_the_Giant_Egg_(GameCube)#Unseen_Behavior