Two or three types work well
While you could simply copy one of your big creatures, you could also copy any mana rocks you have and have Moritte become a snow version of it which then gets untapped by Jorn for an even bigger ramp
For example, if a player exiles three cards from their graveyard to cast Skeletal Scrying, and you copy it, the copy will also cause you to draw three cards and lose 3 life (but you won't exile any cards from your graveyard)
There's zero chance whatsoever that these cards are real
But after enough trial, error, and a few accidental overpays, Ive figured out where the odds are at least somewhat in your favor
If both targets are illegal, the spell won't resolve at all