Cornimer

Cornimer is a tortoise in the. He only comes out during the Acorn Festival in, and gives you mushroom furniture, walls, and floors in change for acorns, which are obtained by looking under oak trees during the festival. However, if the player gives him a rotten acorn, he will say that all the other acorns the player gave him that time don't count. Much like Tortimer telling the player's fortune by using fireworks he can tell the player's fortune by using acorns, as shown below. He gives the player pieces of the mushroom series, each time wanting more acorns.

Theory
Some fans believe that Cornimer is Tortimer dressed up. Although some people think he is Tortimer in disguise, and others think he is a relative or a friend, the strange thing is that during the Acorn Festival you cannot see Tortimer behind the desk in the Town Hall. Another piece of evidence that Cornimer is possibly Tortimer is that when the first time Cornimer laughs in his dialogue towards the player he says "Hef Horf Horf... Wait no! Good luck Lil' Oakie!" The ONLY difference in appearence between Tortimer and Cornimer is their heads. They both have the same shell, cane, and bow tie. Their names even sound similar. Another factor towards this theory is that Tortimer loves to prank the villagers and the player (like on April 1st of Animal Crossing he gives the player an unusable video game).

Other Aperences
Super smash bros. Brawl. Cornimer appered as a sticker in the game Super smash bros. brawl.