Vegemite on toast, and he gets it on his clothes.
When I eat Vegemite, use or hear words like "walkabout", "avo", "loo", "dunny", and "cuppa".
When I've spent hours in the company of other Australians (i.e. during the roadtrip) and suddenly have to talk with a North American and stumble a little as I remember to use the correct vernacular (gas/petrol, restroom/loo, diaper/nappy, etc).*
When I see beautiful photos of wildlife and feel... (I can't actually put my finger on it, but "a connection" is close to it) warm and fuzzy when I see kangaroos.
Here are some more beautiful photos (thanks for sharing Granny (my Mum)).
*I should also point out that I feel like a citizen of the World when I nail the lingo and am able to guide my parents through a US encounter.