You know you see things sometimes and think, hang on that can't be right and need another look and it confirms everything that you've suspected about your lack of sanity?
And you know sometimes you shouldn't say what you think you've seen but you've been questioned about it?

Driving past the Fanny on the Hill pub, it has one of those old fashioned pub signs that swings from a post and a light on the top of it, I was convinced I saw something.
And was so busy trying to rationalise what I'd thought I'd seen that I nearly drove into the curb.
"What where you staring at?" Enquired Driving Instructor No4.
"Oh, I thought I saw a monkey on top of the pub sign."
Cue hysterical giggles from the both of us for the rest of the lesson and comments about watching out for the elephant on the top deck of the 89 bus and hippos on motorbikes.