Original ATK and DEF

From Yu-Gi-Oh!

The Original ATK and DEF are the ATK and DEF Value of a Monster Card before any Monster, Spell, or Trap Cards alter the value. They are the ATK and DEF values listed on the card.

Certain monsters original ATK and DEF are determined only when the monster is summoned to the field; when cards like Chimeratech Overdragon are summoned, its original ATK and DEF is dependant on what was used to summon it. Cards whose ATK and DEF are determined by these factors usually have ? (Or in some cases, 0) where their ATK and DEF should be. Additionally, if these monsters are removed from the field, and re-summoned, or flipped face-down and back up again, this resets their ATK and DEF. Thus, their ATK and DEF would then be treated as 0.