Any phrase that ends with "... on crack," much like any sentence that includes the phrase "the ___ from hell," should be ceased and desisted immediately. I'm not sure if "... on crack" was ever that funny, but I'm certain it's not anymore.
Besides, it's insulting to crack addicts. How do you know what they're like when they're high? Maybe they're quite mellow and very reasonable. Please don't base your opinion solely on Chris Rock's Essence Award-winning performance in New Jack City.
You know, I feel kind of sorry for crack addicts—unlike heroin addicts, they don't have a cool movie like Trainspotting to hang their hat on. Remember that part with the dead baby on the ceiling? Or that scene where Obi-Wan has to feel his way through his own feces to find some lost suppositories? Hilarious! Man ... junkies sure do get into some crazy shit. I should write a pilot treatment for a sitcom.
Anyway, statements such as "That was like Sunday school on crack" or "He's like Dick Tracy on crack"—nope, sorry, just not feelin' it. Let a royal decree go forth! (Go ahead and respond with "You're like Julius Caesar on crack." See where that gets you, smarty-pants.)