Adding legs to the drawing of a snake

The book entitled "Memoirs of Warring States" recorded a fable as follows:

After praying and offering sacrifices to his ancestors, an aristocrat of the State of Chu gave away a pot of wine to his subordinates who helped in the ritual.

Since there were several of them, they conferred amongst themselves and agreed that the single pot of wine, while good enough for one person to drink to his heart's content, was not enough for several persons. They then decided to compete for the wine by drawing snakes on the ground. The one who completed the drawing first would win that pot of wine.

One of them finished drawing the snake first and was taking the wine pot ready to drink it when he saw that all the others had not finished drawing yet. He was too happy and became confused. With his left hand holding the wine pot, he decided to add a few legs to the snake he had drawn.

While he was drawing the legs, another person had completed his drawing of a snake. The other person took over the pot, and said bluntly, "The snake has no legs. How can you add legs to the snake that you have drawn ?"

After saying this, the man happily drank the wine.

When a person tries to be too clever by doing or saying something more than necessary, he can be said to be "adding legs to the drawing of a snake."