Thoughts are only thoughts, there are not there to be entertained by any means. It would be extremely silly if you as a person or rather a human started materialising every thought that your mind came across. Its all about self control.

Thoughts come from your actions, in buddhism they say that your thoughts are influenced by past life actions. Which mean that something bad could have happened for bad thoughts to come to you. Either way this information doesn't matter which is why you don't even know it. What does matter is that the universe is sort of trying to help you take control of yourself and your actions so that you can be a stronger individual. But of course being a human, you have freedom of choice to do what you please. (Beauty of life)

We all have thoughts from time to time like this but try not to regard it as 'annoying' or 'menacing'. Just regard it as a thought. Let it come to mind as it pleases and observe it. Smile at it, and then go in front of the mirror and do a silly dance. So once you learn to start treating it like this it will slowly subside and it won't be there anymore and you will even miss it.