Animal Crossing-e came in four series and was released on the e-Reader in 2002 and 2003. Each series contained an insane amount of cards, though each pack only came with five. It was a goal of players to collect every card in the series. Each card contained a character, design, town tune and more. With the cards you were able to unlock new content within the GameCube game Animal Crossing. They served no other gameplay purposes. Some cards are more rare than others, and it's a goal of some collectors to find them all, just as it is a goal to collect all of the items within the game.
You can receive items in one of three ways. The first way is to send the password contained in the card to a villager via a letter. Within a couple of days they'll send a reply with a piece of furniture. If you send the password to the villager that is featured on the card, then they'll send you a Nintendo Entertainment System game. This is rare, though, because there's a slim chance that the villager is in your town. If you scan the card in the e-Reader while attached to the GameCube at the Post Office or Tailor Shop, you will instantly get a letter in the mail with a piece of furniture. However, depending on the card, the results will differ - you may not always receive a piece of furniture. Other possible results are listed below:
Town Tune card: These cards, which are found in series 1-3, will give you an exclusive tune when you scan it near the Town Tune Board next to the Post Office.
Design card: Found in series 1-3, these cards will give your character an exclusive design, some of which are Nintendo focused. You can receive the design by scanning it next to Mabel.
Mini-game card: This can only be used on your Game Boy Advance. It'll load a game onto the GBA that you can play. Found only in series 2-3.
E-001 (K.K. Ska) - This card came packed with every e-Reader. When scanned, K.K. Slider will appear and welcome you to the e-Reader and Animal Crossing-e. With this card you can receive the K.K. Ska song if its connected to the GameCube. If not, you'll get a password for a Gold Stereo.
E-002 - This card was available in the December 2002 issue of Nintendo Power. When scanned at the tailors, the player would receive a design of an NES styled Link holding a Triforce.
A-061- A card that was made available exclusively at GameStop for free. It didn't contain anything out of the ordinary, though was free of charge, similarly to Air Hockey-e.