how to make a cat gag

i discovered i could make my cat gag by running my nail along a comb. i think its the sound he doesnt like. he didnt seem to mind too much otherwize he would of ran off. i did say sorry by giving him treats. i also discovered he gags when u turn the dial on them watches that have a spinner outer ring on the face. hope you enjoy the video. please note i do love my cats and thort this was unusal so thats why i done it. not in a cruel or evil way.