Beta refers to a stage in a game's development. It is the software development phase following alpha. It generally begins when the software is content complete. Software in the beta phase will generally have many more bugs in it than completed software.
List of Beta Elements in Animal Crossing
Blazel
“Whuzzat?! Blow me down! If ye're goin' to be like that, then ye can just scrape me barnacles, ye siren!!”
― Blazel's only line, Animal Crossing through hacking
Blazel is a beta squirrel villager in Animal Crossing. He can only be accessed by using an Action Replay code. The name "Blazel" is an unofficial name, based on the fact that his appearance combines features of Bliss and Hazel. His official name is 
ù«–•B¡¡. His only actual line comes straight from Kapp'n's dialogue.
"Blazel" exists as two different character entities, one under E15A and the other under D06C. Blazel uses one of Kapp'n's lines at first, eventually using villager lines where he is often mistakenly named Jambette. Its personality is listed as cranky in the game files.
Appearance
Blazel's fur is colored red, and his eyes are large and blue; similar in color to Bliss' eyes. On his tail, he has a creamy white pinstripe, like Hazel does. In addition, he has another creamy white swirl on his head that resembles a question mark. He wears a Latin Uniform as his initial shirt.
Gallery
Blue Fish
The Blue Fish is a beta item in Animal Crossing. It is simply a blue fish with a hook in its lip.
Although it's purpose is unknown, it is suspected it was used to test fish items or fishing. It has many item numbers.
DUMMY
The DUMMY is a beta item that is only available in the original Animal Crossing.
A player places a DUMMY in his home.
When placed in the player's house, it appears as a floating white triangle with red Japanese characters in the center reading "ダミー." The characters, when translated into English, read "dummy." It is widely considered a glitch item, since it cannot be sold nor does it appear in the catalog.
As it can be placed as an actual item, it is assumed that it was a substitute item for real furniture during testing of the game.
It is only obtainable by talking to a villager inside an Igloo through specific conditions. It can be awarded through the "pick two cards" game. One card results in an item that must be purchased with Bells, and the other card will award a free prize. This free prize card is occasionally the DUMMY.
Glowing Yellow Box
The cubes pushing the player outside Nook's Cranny.
The Glowing Yellow Box is a beta item in Animal Crossing, possibly a beta for the Lighthouse. It is a yellow cube that shifts from side to side, changing its color to brown and back every once in a while. It can alter where the paper airplane spreads to, and can push the player, sometimes causing them to "fly" and stand on top of the cube. This beta item can be seen in Animal Crossing's Beta World 01, when used with cheats.
The index number for the glowing yellow box is 8003.
Paper Airplane
White airplane.
The Paper Airplane is a beta item in Animal Crossing. It cannot be obtained without the use of cheats.
The reasons for its removal are unknown, but the item still remains in a buggy state. When added to the inventory, it acts similar to a piece of paper, giving the player the option to "Read" or "Write a Letter". It is invisible when dropped, but running out of the acre it was dropped in and returning causes it to appear. It has the ability to spread and shut down acres. It may spread throughout the entire town, rendering the game unplayable. The areas it spreads to are altered by the Glowing Yellow Box.
Paper airplanes.
Sickle
The sickle is a beta item for Animal Crossing. It is in the game's programming and in the Animal Crossing guide, but it cannot be obtained without hacking or using the Action Replay, as it was never completely programmed. When obtained, it can be found in the player's pocket and appears as a net. When equipped, it looks as if the player is holding nothing, as well as acts like they are holding nothing, but on the pocket menu when the cursor is over the player the game shows that they are holding it. When dropped, it appears as a toolbox, which appeared in Animal Forest, Wild World, and New Leaf.
Unknown Item
An Unknown Item in the player's inventory.
The Unknown is a beta item in Animal Crossing. The item when placed consists of a floating triangle with the Japanese word (ダミー, Dummy). It resembles the DUMMY, which can be received by going into the winter igloos and receiving the gift from the igloo's animal, and may be the "English" equivalent.
As it can be placed and functions as a proper furniture item, it is probably an old testing item to substitute actual furniture inside the house.
List of Beta Elements in New Leaf
The following are only seen in the original 2010 screenshots:
- The cliffs were a lot different: wavier than the actual cliffs.
- In the dialogue box, the villager's name is written a lot smaller.
- The player houses look more like released villager houses than in the final release, and there is no paved exterior bar a hedge closely fitted to the house.
- The bench is surrounded by an oval of pavement, as is the street lamp.
- The player is able to look down on a villager walking on the beach with the vilager actually noticing them and looking back. This rarely happens in the actual game.
- Villager houses are the same as in previous games.
- Flowers and bushes appear to be a lot more abundant.
The following are only seen in the 2011 E3 trailer:
- Originally the villager speech boxes were rectangular, rather than cloud-shaped as in the final release.
- The cobblestone bridge was darker.
- Rosie's house is more similar to her Wild World house. It evidently hadn't been redesigned yet.
- The Dock was slightly longer and was more of an L Shaped design.
- Sounds, such as the sound when a tool is equipped or the sound when clothing is changed, were the same as in Animal Crossing: City Folk.
- Trees, flowers, bushes, and other plants had a shape different from the ones in the final release.