The Cutty Wren was a tradition among Welsh morris dancers. According to Isiah Saul, Middleton was the only English location that followed the tradition.
As part of the tradition, a wren was caught and killed, then paraded through the town. In Middleton, the morris dancers used an alien artefact as their wren. It began to drain energy from the dancers, but the Second Doctor and Isiah freed the "wren" and sent it back into space. (PROSE: The Cutty Wren)