Final answer:
In the book 'Wonder', the made-up person with really gross habits is named Beulah, who features in a game played by the protagonist and friends.
Step-by-step explanation:
In the book Wonder, the made-up person who has really gross habits is named Beulah. This character is completely fictional and is part of a game that the protagonist, Auggie Pullman, and his friends play, where they make up fake identities for themselves with specific characteristics. Beulah is known for her disgusting habits, which are humorously exaggerated for the game.