Cleese delivered what he called "a random act of flowers" to patrons and friends at the Center on Halsted.
The "Monty Python" star was also stunned by rare gun violence in his native England where politician Jo Cox was shot and killed in broad daylight.
"Its never happened before in my lifetime," he said. "So in this time of crisis when there's so much needless violence, these little acts of kindness begin to reverse the momentum."
Cleese said the flower deliveries aimed to bring cheer to those who feel most vulnerable.