With season 5 of the cartoon masterpiece recently released on DVD too, finding only this Christmas bonus (or as stingy Mr. Burns would say, ''Christmas boni'') in your stocking might be a disappointment. Not only are there just four episodes in The Simpsons Christmas 2 (plus an animation feature) but just one, '''Tis the 15th Season,'' qualifies as a real Christmas show. The others are charmingly Simpsonian, but digging up eps with genuine Christmas cheer was clearly a struggle for the creators. In ''Homer vs. Dignity,'' Mr. Burns hires Homer as his personal ''prank monkey'' until Homer finally finds his backbone during the Thanksgiving Day parade. The snowed-in students of Springfield watch a ''classic mirthmaking'' Christmas film in ''Skinner's Sense of Snow,'' and in ''Dude, Where's My Ranch?,'' Homer's frustrated attempt to pen a Christmas carol yields a chart-topping anti-Flanders anthem, covered by William Shatner. Halloween, as any Simpsons fan can attest, is the show's favorite holiday, and this DVD feels more trick than treat.