I read somewhere (I think maybe David Baboulene’s The Story Book) that when you think of an idea, don’t stop, rather think again and try to come up with something more original. I.e. the first thought will probably be a cliché or boring idea, so take it a bit further to get to a better one.
But I want to take it a step further and say that you should always look for the extreme. Never settle for the middle or the safe. Pick the craziest idea you can come up with and run with it, no matter how ludicrous it feels.
Think about it, if Bram Stoker had thought that crazy blood-sucking baby-eating creatures of the night were too ludicrous, where would we be? If George A. Romero had thought zombies were too weird to put in a film, where would we be? And finally, if Mary Shelley had decided to stick with something normal, there would be no Frankenstein(‘s monster).
The point is, everything seems crazy until you get used to it. In fact, you will think your own things are crazier than other people will think your things are.
So go on and pick the weirdest, craziest idea in your head. Pick the extreme and go with it. You’ll be happy to see where it leads, or at least you’ll be in for a hell of a ride.