Yeah, the "playing an Item card to no effect" thing.
From what I understand:
- I can't use
Energy Retrieval (BW) if my discard pile has zero basic Energy cards, because using it without any basic Energy cards in my discard pile would be playing Energy Retrieval with no visible effect other than wasting the card.
- I can use
Super Rod (NVI) if my discard pile has zero Pokémon cards and three basic Energy cards or zero basic Energy cards and three Pokémon cards.
- I can use
Pokémon Collector and search for zero basic Pokémon cards, since it says "up to three".
- If I have seven cards in my hand, I can use
Copycat even when my opponent has zero cards in their hand, since shuffling hand into deck is an effect that changes game state in a way other than using up the card.
- If I have zero cards in my hand, I can still use Copycat even when my opponent has zero cards in their hand, since the shuffle is still required even if I have zero cards in my hand.