How casual australians act around local wildlife was the most surprising thing for me (german) when I went there.
Lots of little Jellyfish in the water close to Sydney harbor? Guy walks into the water, picks one up with both hands, walks up to us like "guys I haven't seen those before, anyone know what kind that is?".
Cliff jumping with aussies, see water below us foam up a bit. "Looks like sharks. Ah it's probably just small ones, they won't do shit". (Fun fact: that was the exact cliff jumping location of this (faked) video)
Big ass spider inside a construction site I was working on. Like, big enough to drop a magical sword if you kill it. Asked my boss about it. "Nah leave her alone, it's the house spider. She's not dangerous!". When I asked whether "not dangerous" meant those kinds of spiders aren't venomous he answered "Nah we'd still have to drive you to the emergency room. But like, not as fast as we'd have to with other spiders". Ok thanks boss.
Stuff like that really makes me wonder how many of the people I've met there are still alive today.
I remember getting off the plane and just noticing that the colors were all different. Felt like the sun was brighter and the sky bluer. (might have been because we left Germany in winter and arrived in summer) but also, the silvery green of the Eucalyptus trees is a color we don't get here.
Also: Free BBQ stations everywhere. That was cool!
Moved to country Australia from NZ at age 14, and of all things I remember being astonished at how f**king huge the sky seemed, because the land was so flat and vast compared to where I'd come from. The horizon just stretched on forever!
Went in to buy more appropriate footwear in my first few days, and I was convinced the shopgirl was flirting with me. Bought something else in another shop, and more flirting. Another shop and the same thing.
Turns out they weren't flirting. They were just naturally being really friendly. Smiling and being interested in me for no other reason than because that's just how you do things.
I ended up taking a job going door to door selling things (backpacking yay!) and I was amazed how few times I was told to f**k off.
To explain, in the northern hemisphere when the moon is waxing, it fills up from the right side to the left, then when it wanes it goes from the same direction. In Australia, on the other hand, the waxing crescent starts on the left.
It took me a moment to realize what exactly I was seeing, and I was absolutely tickled pink once I figured out why it was the way it was. :)
Every time I've ever met an Australian on vacation (especially in Bali) they have been drunk and screaming. Its been the case so often in so many places I thought that everyone from Australia was like that.
The biggest shock to me was driving around and seeing a (presumably) roadkill kangaroo. Now it makes perfect sense when I think about it but prior to going to Australia the only time most people ever see a kangaroo is in a zoo all safe and in an enclosure so you kind of figure it's like that all over the place.
They're kind of like deer, just running around and getting hit by cars.
Bonus (totally unrelated) story: I couldn't believe you guys sell and eat kangaroo meat. I guess it goes back to my previous point about kangaroos being like deer.
Visited Australia and New Zealand two years ago. The most unexpected, most jarring thing I've seen is how disciplined the people are compared to my country, sadly. It was really peaceful, clean and quiet. A breath of fresh air, literally and figuratively.
The price of food, especially produce. At first I thought it was because so much would have to be imported, but the vast majority of produce I bought was from Australia. I discussed this a bit with some Australians and Americans and we wondered if this was the real cost of food, if you pay everyone in the chain an actual living wage, instead of depending on underpaid migrant workers.
The gulls are SUPER aggressive. Those bastards get a foot away from you, yell at you, and then 3 distract you while one steals food off your plate. (They actually got a piece of tuna off my wife's plate this way.)