Whenever anything is foreign to us and we feel like it's out of the ordinary or strange to do something, we feel like imposters. In fact, this is a natural phenomenon. When you partake in a new achievement-based tasked, and it's new to you, you'll feel like an imposter.
You'll feel like you don't fit in. Like you're not good enough, smart enough, funny enough, or whatever. That's just the psychology of the mind. However, achieving anything big means pushing through those uncomfortable feelings.