The New Coat Surprise
Treat yourself to a new coat and some fancy underwear.
Turn up at his (getting a cab there is probably best) and go inside, telling him you need advice on the coat.
Sit him down and get his opinion. He likely will be complimentary, but a little confused, which is how you want him.
Juice the situation, and then carelessly remove the coat to reveal what’s underneath. If experience is anything to go by, his jaw should hit the floor.