What's the silliest mistake you've made in the Level Editor?

[raptorhunter6]

Well I just recently begun using the Level Editor, but I made 2 rooms and put a Grunt on the second room. So I go test out my map and I am greeted by the "Gwah!" Of the monster and then the "BEEEEEEP!" Sound from the monster spotting me but it was coming from behind me and I get hit 4 times at once and I was Confused, Scared and well confused. Turns out I accidentally created 4 Grunts Right on my Start Area -_-' . Yeah pretty stupid.