A 5 Mexican peso coin looks the same as a Canadian $2 coin (toonie). I got a coffee at Tim Hortons and they gave me one thinking it was a toonie. I still have it on my desk at work lol.

Canadian quarters and pennies showed up fairly regularly, and everyone tries to get rid of them in vending machines. Never saw pesos, and I lived 100km from MX.

Or any countries next to each other

I assume Canadian/USA coins and Mexican/USA coins turn up in each others places sometimes.

Apart from the usual NZ coins, I've gotten a Fijian 5c piece, a Malaysian 10 sen coin, and a Saudi coin I got no idea what it's worth. Same size as a 10c coin.

What foreign currency have you gotten as change from the shops in your countries by accident?

will be in NZ soon enough. I'll go with Kiwibucks for you.