This sign (in a second-hand furniture shop) was not even funny to my Australian boyfriend at the time! While my German girlfriend agreed that climbing on furniture signs would not normally occur in Europe.
This sign is not funny unless you know that it is located on the Great Ocean Road - miles away from the nearest airport, so you'd kinda expect that if a tourist has taken her/himself this far, by now s/he had realised that it's left hand traffic in Australia.
NOTE: This website is written in British English, which is the English we use in Australia. You will find words like "traveller", "harbour" and "realise", and they are all correct in the language used in Australia.