Some cards that kids traded for lunch money in the '90s are now selling for hundreds of thousands or even, yes, millions
If a spell is copied, choices made while casting it are copied, so the copy will have the same abilities spliced onto it as the original
For example, if Narod, the Beige Flower and Doran, the Siege Tower ("Each creature assigns combat damage equal to its toughness rather than its power") are both on the battlefield, each time a creature would deal combat damage, that creature's controller chooses whether it assigns combat damage equal to its mana value or its toughness
Essentially, Dialga is used to stack Yanmega ex with Energy here, but they can also be used as an attacker too where necessary
If you pull it: Congratulations, you just won the lottery