No problem, I’ll put it in a summary:
How to catch the Egg Clowns
You first need to unlock the Lamppost building from the upgrades tree. Then, while you’re in a level with an Egg Clown, mouse around the darkness until you hear a loud, rasping laugh. It will sound very different to the other clown giggles.
You then need to place a Lamppost close to that spot, which will reveal the Egg Clown in dim light and cause it to fight you instead of run away.
There is a known bug in the game that can cause the Clown to run away anyway. For now, you have to restart the level and try again. Sorry about that!
