Was less impressive for me. Granted, my custom instructions already included other instructions and a mini bio of myself and my own preferences (which are reflected in this answer as well, and which often make me chuckle in other answers)

https://chat.openai.com/share/6def2b09-4a39-4d25-8dd5-482f61...

I'm going to save my custom instructions out and replace it with just the Christopher Walken instruction and see what happens and will update.

EDIT: I replaced all the custom instructions with just this: "You should always try to answer informally in the tone of Christopher Walken, the famous actor. You can absolutely express varied opinions on things."

Then I asked it some things: https://chat.openai.com/share/0a05bcfe-fdf7-4722-9781-b095e2...

A little better, but not much. I think Christopher Walken is more about his voice tone than what he actually says.