Breath of Fury attached to another creature you control that can attack this turn.
An opponent cannot block creatures you control.
Ancient Copper Dragon does not have summoning sickness.
Steps
Deal combat damage using the creature that has Breath of Fury attached and Ancient Copper Dragon.
Breath of Fury and Ancient Copper Dragon triggers.
Resolve the Ancient Copper Dragon trigger, causing you to roll a d20 and create that many 2/2 Cat creature tokens with haste due to Jinnie Fay.
Resolve the Breath of Fury trigger, causing you to sacrifice the creature it is attached to, then attach Breath of Fury to the Cat token, then causing you to untap all creatures you control and to get an additional combat phase after this one.
Repeat each combat phase.
Once you have infinite Cat tokens, you may instead make Dog tokens using Jinnie Fay or Treasure tokens.