Back when I was the "new guy" code monkey at a fairly sizeable brick-and-mortor-and-e-retailer, I let the intrusive thoughts win and did some impromptu QA on the e-commerce site. (In the test environment. Don't worry.)

It handled things like trying to put "0" or "-1" or "9999999999999" or "argyle" quantity of an item in the cart just fine.

But I know my 2's-compliment signed integers. So I tried putting "0xFFFFFFFF" quantity of an item in my cart. Lo and behold, there was now -1 quantity of that item in my cart and my subtotal was also negative. I could also do things like put a $100.00 thing in the cart and then -1 quantity of something that cost $99.00 in the cart and have a $1.00 subtotal.

(IIRC, there was some issue with McDonalds ordering kiosks at one time where you could compose an order with negative quantities of things to get an arbitrarily large unauthorized discount.)

The rest of my team thought I was a fucking genius from that moment on. I highly recommend if you're ever the "new guy" dev on a team and want to appear indispensible, find a bug that it would never occur to a QA engineer who doesn't have a computer science degree to even test for.