Is it OK to ask a celebrant to wear a costume at our wedding?

Hello! I've read some responses to celebrants dressing in a matching style etc. Is it rude to ask if they wouldn't mind wearing a costume? I've read somewhere a couple got married by batman and then the obvious Elvis option.. I like the idea of an iconic character and think it would be something to remember but wouldn't want to offend anyone or make it a bad experience. TIA