He sits near the entrance of South Tower, and people shower him with vibuthy or holy ash and pray.
He is the largest Ganapathy within this temple and today, special pooja or prayers will be performed. Extra large modhagam (rice based cake) will be offered to Him and later distributed to the public.
Narthana means dancing, this dancing Vinayaka is near the Mottai gopuram and people pray to Him on special occasions like Sasthiaptha poorthi (60th birthday).
Couples who are not blessed with a child are advised to do milk absheka (bathing the deity with milk) for this Narthana Vinayaka. Though many beliefs sound superstitious, at times, out of desperation and yearning I tend to believe in age old customs. Belief is everything, I too have done milk abeshikam here, as I had my kid only after a long time.