Well, first one that comes to mind in this country is the Outspan Mini, resident at Beaulieu Motor Museum IIRC:
As you can see, the Outspan car is shaped like an orange, has orange skin-textured bodywork, looks like an orange - but is, in fact a Mini! Admittedly, a highly modified Mini.
The car has a top speed of 30 mph. At more than 30 it is unstable, and can roll over.
As you might expect, the car is a great success with children.
The Outspan Mini lives at the National Motor Museum at Beaulieu, but seems to get around quite a bit. It's done the HCVS Brighton Run more than once.
Six of these customised minis were commissioned by Outspan from a company called Brian Waite Enterprise Ltd. based at Bodium in East Sussex. They were built between 1972 and 1974, and were used on advertising campaigns both in this country and in Europe. One of the six is known to live in South Africa these days.

Some people are like Slinkies - they serve no useful purpose, but they still bring a smile to your face when you push them downstairs.