What is the strangest thing you've ever thrown in a pot roast?

Over the years I’ve perfected my pot roast. It’s to die for. My most recent addition (about 10 years ago) was tomatoes at my four year old grandson’s request. I thought it was weird, but complied…and the was the best culinary move I’ve ever made! Can’t do pot roast without it!
Well, started some today…had some still-fresh left over Portabella (sp?) mushroom in the fridge. Threw them in….I’m not sure this was a good thing! I guess I’ll find out.
So what experiments have you ever tried, and did they work or did they crash and burn?