My 4 year old decided he wanted a Grinch Who Stole Christmas Costume 6 months ago. With some help from grandma we created the coolest Grinch costume for him. I special ordered some lime green monster fabric and a Santa suit. Then I made some grinchy finger gloves and elf shoes.
He carries around a Santa sack for candy. He did such a good job when we fabricated a latex “grinch” nose and painted his face green. Start to finish, the costume took about 15 hours total, and “with this coat and this hat, he looks just like Saint Nick!”