Truly, ''D--- in a Box'' is the gift that keeps on giving for the Lonely Island, the nom de fake rap of Saturday Night Live star Andy Samberg and his BFFs, SNL writer-directors Jorma Taccone and Akiva Schaffer. Since that brilliant, indisputably instructive R&B satire first appeared in 2006, the trio along with featured players like Rihanna, T-Pain, and a very game Justin Timberlake has had remarkable success in the notoriously difficult genre of ''funny music,'' hitting a neat balance of parody and sweet-natured homage (peppered with plenty of references to their respective junk). Now, two years after Incredibad, a debut that collected many of the group's greatest, previously televised hits, comes Turtleneck & Chain, a perfectly acceptibad follow-up. On ''Motherlover,'' honorary Islander Timberlake returns for a deeply filthy, proudly MILF-y ode to ''pushing that way where you came out as a baby,'' while the triumphantly goofy ''I Just Had Sex,'' with Akon, manages to be both outrageous and entirely plausible radio bait. Rihanna, Nicki Minaj, a sleepy, maybe-not-in-on-the-joke Snoop Dogg, and ''major cinephile'' Michael Bolton(!) all make appearances but it's the chameleonic core trio that truly surprises. At one point, over a classic, adrenalized hip-hop beat, Samberg and Taccone trade fierce criminology rhymes with a swagger that's downright serious. Until, of course, one notices the title: ''Trouble on Dookie Island.''