You cannot Special Summon from the Extra Deck, except Fusion Monsters, the turn you activate either of this card's effects
Deckbuilding implication: you need mana consistency , defensive interaction , and finishers that end games instead of generate value. Good questions: Can I reliably cast my top end
Attach 2 lightning energy from your discard pile to that Pokmon
Others even help you fill up your inkwell so you have more ink to use for bigger plays
This allows you to slow down a game until it benefits you to play more than one card a turn, or you can finish a game with direct damage
However, they can still be raised and used like any other Pokmon, and there are tricks that let you retain both of them permanently: transferring Kenya's mail to another Pokmon and handing that one over instead (the remakes will even give your Pokmon back if you try this) and reaching a high enough friendship with Shuckie