I think the fact that it was an interview does not determine what language formal or informal should be use. It's the person who is the guest determines that. For example, with a youtuber, you can make informal interview and even use slang etc. But interview with the Queen, or a person who is,let's say a president of some country, that's definitely a formal language situation. And I don't know if show up is considered informal. I'm really looking forward to seeing some natives reply to that,maybe muy response could bump the post ;)