The Xbox One has a HDMI port for television, so plugging an Xbox 360 into it should work. Is this possible without damaging anything?
Yes, plugging the Xbox 360 into the T.V port on your XboxOne will allow you to have both running with sound and visual. Even the Xbox One stereo connector will play the 360's sound through the One's controller(stereo connector connection). " http://support.xbox.com/en-AU/xbox-one/system/compatibility-with-xbox-360" Edit; However, video lag makes gaming at fast speeds pretty much unplayable due to the delay on the controller to the video delay of the display lag.