"This is a time travel pay phone," the sign calmly states on a phone booth somewhere in Sydney, Australia.
Before you ponder the menu, offering to take you back 15 minutes, "2 weeks before they all found out what you did" or simply to "Dinosaurs", consider this: would you use it if you could?
The sign is one of the many irreverent pieces hidden throughout Sydney by mental health worker Michael Pederson.
He told The Huffington Post Australia he wanted to make people smile, but that wasn't all of it.
"I guess when you're doing anything in public, humour is a quick way to engage people," Pederson said.
"I hope it brings up ideas as well -- gets people thinking about their headspace."
Pederson said that while he'd dabbled in painting in the past, he wasn't interested in being an artist displayed in galleries.
"It's not something that I want to pursue," Pederson said.
"It has its presence in the outside world. Sometimes it will be removed in an hour, sometimes it will last a month."
He said you'd be lucky to catch him in the act installing a work.
"Generally I don't like to stick around too long," Pederson said.
"It looks a bit creepy I guess. Sometimes I'll watch to see if anyone notices, but generally I'm pretty quick."
Check out some of his work below or see it all at his website Outside.