Ethan Shanfeld Stephen Colbert is channeling his inner K-pop with a BTS-inspired music video featuring Jon Batiste and the Stay Human band, as well as a cameo from Alan Alda, that aired during yesterday’s “The Late Show with Stephen Colbert.”In “Excuses Song,” Colbert — rocking a middle part and soul patch — croons about potential excuses one can make when invited to unwanted social events.After being the subject of one of the excuses — “Tell ’em that you’re with Alan Alda” — the legendary