I'm reading Phantom Armies of the Night - The Wild Hunt and the Ghostly Processions of the Undead by Claude Lecouteux. In it, it claims that the dog and rooster were attributes of the Celtic Dagda. This would seem to tie the Dagda to the Hellequin or Hannequin (later Harlequin) who lead the Infernal Host/Wild Hunt.
I can't find any reference of dogs or roosters being attributes of The Dagda outside of this book. Would anybody know of any information that would confirm this?