Later in the game you should be able to pay the escape cost, especially if you have any amount of self-mill (dredge, Im looking at you)
If it has an ability that triggers at the beginning of the end step, that ability will trigger for Identity Thief and not for the returned creature
Fortunately, the game engine allows interaction via attacking and blocking for them and the rewards for winning the battle are in casting card types already in the game
It just does The Thing for a single generic mana that any deck can pay for, and is thus worth highlighting
Furthermore, cards from the Commander precons, Through the Ages , and promotional/ Secret Lair cards are ineligible for consideration
However, Ditto rarely appears in its blue shiny form, giving this "baby shiny" an unusual artwork to appreciate