Originally Posted by smartcooky
Short(ish) version : way back in the days of USENET there was a group called alt.fan.warlord which specialized in making fun of people with overly large, garish signature blocks, often festooned with horrible ASCII art. One of the recurring targets for some reason were people with signatures which had large maps of Australia in them, and the claim was that the city most often marked on those maps was Perth. As time went on the joke became taking someone's mess of an attempt at an ASCII art car or dog or whatever from their signature block, and dropping in a random asterisk with an arrow pointed at it and labeled as Perth.
example (stock ASCII art of a cat which gets messed up when trying to copy/paste) :
`-.-' \ )-`( , o o)
`- \`_`" *<---Perth
Basically a way of saying "your attempt at putting an ASCII topless Jerry Ryan in your signature is so awful it looks more like a map of Australia, and you'd neglected to point our where Perth was.