Os Mutantes has been a band on and off since the mid-’60s, having begun life as a psychedelic rock outfit before morphing into one of the faces of the Tropicalia movement (and then morphing right out of the public eye). A reunion in 2006 reignited interest in the Brazilian band, which has been relatively active since. They agreed to stop by the A.V. Club studio while in Chicago recently to give us a Brazil-ified version of the John & Yoko/Plastic Ono Band holiday anti-war classic “Happy Xmas (War Is Over),” including a couple of extra Mutantes-specific lyrics. The group’s latest album is Fool Metal Jack. Oh, and this is the first Holiday Undercover of 2013—there will be a total of four this year!