I'm sort of surprised there hasn't been that many attacks in human history on April 1st. Noone would believe it, until it was too late.
"Sir we are under attack!"
"Real funny, Johnson"
"I'm serious!"
"Yeah, yeah...let me just call up the president on my imaginary phone"
"Look at the radar, sir"
"I'm calling...I'm calling...yeah sir? we are under attack by Canadians, unicorns and mermaids...its a bloodbath!"