upset the/somebody's apple cart
upset the apple cart
Fig. to mess up or ruin something. Tom really upset the apple cart by telling Mary the truth about Jane. I always knew he'd tell secrets and upset the apple cart.
upset the apple cartwreck an advantageous project or disturb the status quo.
The use of a cart piled high with apples as a metaphor for a satisfactory but possibly precarious state of affairs is recorded in various expressions from the late 18th century onwards.
1996 Business Age The real test will be instability in China…Another Tiananmen Square could really upset the apple cart.