This is when plans are made to do something or a way of doing things has been established, but then some know it all assfuck has to chime in with his/her bright idea. The consequences and repercussions of said assfuck throwing a monkey wrench into the clockworks is what ruins everything that has been running smoothly otherwise. This then causes confusion much like if a applecart would spill out and apples would roll all over the place in a crowded market.
Tony : Why is skippy trying to change the trip plans at the last minute, they were set in stone months ago?
Mike : I don't know that mother fucker is just trying to upset the applecart.