Cards known as the flip cards from the Kamigawa set were so hard to understand in a first glance, that they would never be used again
Since nearly every character card interacts with Puppy cards, bringing a ton of them ends up being really strong, as you will get value out of everything in your deck nearly anytime you use a card
Slot the card in just as you would normally, so that the bottom edge of the card lines up with the bottom edge of the outer sleeve
That's why it's going to help everyone out with mana, cards, and some tokens here and there
If you have very expensive vintage Magic cards, I would definitely look into the larger auction houses as they have the unique advantage of getting you you national attention
Personally, with Kastral, I would choose to give all my Birds +1/+1 counters whenever I deal combat damage