Mr Squiggle easily rates as a definitive children's' TV show in Australia, alongside 'Play School'.
Mr Squiggle himself was "the man from the moon" - in real life, a puppet with immovable mouth and controlled by strings. The most important feature of Squiggle's was his nose - He had a pencil for a nose.
Mr Squiggle went where he was going by his rocket - whom he names, affectionately (even if not creatively), Rocket. When Mr Squiggle arrived, he would meet with the hostess (Miss Pat, Miss Jane & Rebecca, among others) to draw some pictures with her (saying he needed her to hold his hand to be able to draw his squiggles).
The artwork itself was drawn onto cardboard, with some shapes and/or lines already drawn (these were sent in by viewers). Mr Squiggle would then draw his own picture ("squiggle"), building from the existing things. With one catch - he would always draw the squiggles upside-down (occasionally he drew it sideways).
Other regular characters included:
Blackboard - This blackboard had attitude! His constant "Humph, hurry up!"s amused adults and kids alike.
Bill the Steamshovel - He was a bit of a jolly character, always willing to help
Gus the Snail - Gus was an enterprising little insect, even starting his own TV channel! He didn't always have a shell on his back - he usually had something quite different such as a TV or a potplant.
I can't speak for the early years, but in the '80s the show went for half an hour. In the '90s and past 2000 the show was reduced to a five-minute format, with only the squiggles and smallest of story lines. Thankfully, Blackboard survived the culling though :)