Anybody know how to say 'Why so serious' in Japanese?

Question

For a theater project, we were supposed to take a well-known character and change one thing about that character. I took the Joker from The Dark Night and decided to make him Japanese, but I don't know how to say Why so serious? in Japanese. Any help?

Answer 1

no but you could probally find the answer online

Answer 2

nande sonnani majime nano? (casual)