When you realize the total combos of car key possibilities, you have a decent chance your key would work, too!
Back in the 90s, I was on a trip and ended up parked next to a car which had a car alarm that responded to the key fob for my car alarm. It was very disconcerting.
I borrowed my friend's Prius once and accidentally opened the door to the wrong one and got in for a second before slowly realizing things felt off.
It's a keyfob, and it didn't open his door when I tried to get in :P
Had two GM 3500 cargo vans, one a 2002 Chevy Express, the other a 2001 GMC Savannah. Same vehicle different badges. Noticed the keys were a bit similar and found that the Chevy key could in fact unlock the GMC with some wiggling but not the other way around. It did not work in the ignition lock.