The Grinch is a cool idea for Halloween because there’s a prequel to The Grinch called ‘Halloween is Grinch Night’ and it’s a really fun and cool way to bring a little Christmas magic to Halloween. It’s a character and it’s fun. Be prepared though for a lot of people wanting pictures with you.
You will see that the Grinch is a surprisingly beloved character for Halloween, and it’s always fun to see a classic costume executed well. Your success means you have a solid foundation to build on for future themed events.