I have not done a frame-by-frame analysis of the song or anything like that, but for whatever it's worth I have not seen any evidence of such a thing. If such a thing was included then it more than likely was a gag left by the animators. There have been examples in numerous animated films where little artifacts are left in a frame or two. One of the most notorious of these examples was the inclusion of a "questionable" image in the background of a scene in The Rescuers, as confirmed by
Snopes. Thankfully, the inclusion of an animated microphone and pole in LBT 4, if true, is rather tame in comparison to that example.