Doubutsu no Mori e+
The Whale is the name given to the unknown fish portraying a large shadow seen in Animal Crossing and Doubutsu no Mori e+ on a trip to the island. It is approximately 20 times the length of the average Sea Bass shadow and it cannot be caught. However if the player uses a glitch to walk on water, he or she can use the fishing rod to try to catch the whale, but once the whale starts to reel in, the game crashes. 
A now removed YouTube video existed showing footage of the massive shadow between the town and the island. It is possible for the player to catch the whale, but when dropped, it appears as a unused fish icon.