LOL - don't "harsh my mellow," you ungroovy buzzkiller

The "best sentence I read today" (as per Marginal Revolution) contained a phrase new to me, "harsh my mellow." Perhaps it was used ironically; I hope so. Worldwidewords discusses the phrase's etymology. Evidently it's said more frequently after 4:20 and on April 20. It's also the name of an airfreshener.