Dug's Special Mission

Dug is a cheerful, dim, short-legged dog, a walking sausage.

On his birthday, he stumbles between a running bird and three dogs in chase; the bird gets away, and, in exasperation, the pack gives him mindless task after mindless task.

Dug is enthusiastic, and every assignment backfires on the three.

Finally, they threaten him with punishment from their master.

Can anything turn Dug's birthday into a happy day?