Day -- whose character cleans toilets, huffs glue and lives in squalor -- began by acknowledging that he doesn't come from the most prestigious of career paths.
"You will get to receive wisdom, life lessons, knowledge from a man who has made a living pretending to eat cat food," he joked.
Day, 38, offered a series of humorous observations, noting that a cap and gown makes everyone look like a "medieval pastry chef."
But he also shared some wisdom from his own experiences as a struggling actor who became a successful comedy writer.
He noted that "a college degree does nothing" unless you make something of it.
"Don't wait for your break, make your break," he said.
It's Always Sunny in Philadelphia just signed a lucrative deal for season 11 and 12, which will make it the longest-running live-action comedy in TV history.