Commuters on their way into the city this morning have been advised to watch out for wacky and weirdly dressed young people waving rolled up newspapers.
But drivers should merely be careful, not alarmed - it's just the annual Prosh day for students at The University of WA.
Gallery: Prosh pranks
Students gathered before dawn and should by now be dispersed widely across the CBD this morning, selling copies of their annual satirical newspaper to raise money for charities MND WA, Clown Doctors, The Heart Foundation and The Grey Man.
About 115,000 copies of the newspaper are expected to be sold on the streets of Perth.
About 11am, students will flock to the Esplanade Reserve near the river for dancing in the park before a float parade through the city's streets, ending back at the Esplanade for a performance of skits and entertainment for the lunchtime masses.
Female motorist caught twice in 90 minutes for driving while on her mobile phone.