A 10-foot-tall cartoon mural of a doofy man walking an awkward fish on a leash hangs over a mass of morning-after millennials crowding into Crema. Painted by Denver’s Michael Graves, the mural on the chic RiNo cafe is one of dozens of pieces of street art — not graffiti, as Graves would remind me — spattered on the ‘hoods walls, loading docks and food trucks that give it its flavor. But if these murals are art, what’s their story?