Sentence:  The best of friends become the worst of enemies when Barney makes a hilarious attack ad where he viciously pummels a cardboard cut-out of Homer before special guest star Linda Ronstadt joins the fun to both continue the attack on the helpless Homer stand-in and croon a slanderously accurate, insanely catchy <WSD>jingle</WSD> about how “Mr. Plow is a loser/And I think he is a boozer.” 
Meaning of the word marked with <WSD> tags:  A memorable short song, or in some cases a snippet of a popular song with its lyrics modified, used for the purposes of advertising a product or service in a TV or radio commercial.