Simulate different types of weather. Can you fool other people or even some scientific equipment?
Photograph something that is unique and then something that is not unique.
Draw part of a fictitious world...
Lie down in a public place for five minutes.
Measure and record all the spaghetti you eat. Keep a record of what you've eaten the height of.
How far can you travel while sucking the same mint?
Draw a picture of a continuous, 360 degree, view from under one or more trees in a park or wood.
Discover how polluted the local air is by identifying lichens growing on trees.
Put on a performance for a CCTV controller. You could improvise a short play, show off a dance routine or hold a full blown talent show.
Decorate a pizza like planet Earth, then make, cook and eat it.