I went to a wedding yesterday and nearly wore the wrong jacket. My Wee Jimmy Krankie blazer was on the back of a chair in the living room and it looked quite like my suit jacket. I put it on and it felt like my suit jacket. It was only when leaving the flat for the taxi that I had a moment of epiphany and twigged that I was partly in fancy dress. It was enough time to switch to the proper jacket.
But if I'm honest, I really don't think anyone would have noticed. The WJK blazer is actually quite good.