In Bud, Not Buddy why did the people in the food line pretend that Bud's name was Clarence?

In Chapter Six of Bud, Not Buddy, Bud accidentally oversleeps and is late to line up at the mission for his breakfast. By the time that he arrives, the line is already two blocks long. As Bud waits in line, the man who allows people to enter the mission cuts off the line; the folks remaining will not be fed today. Bud tries to argue with the man, but is met with a slap on the hand. However, before Bud can leave, someone grabs him by the neck, calls him "Clarence," and begins to scold him for being late. 

Eventually, Bud understands that these strangers are only trying to help him. They pretend that he is their son, "Clarence," in order to negotiate Bud closer to the front of the line--in other words, the part of the line that will be served breakfast.

Bud is able to receive oatmeal, milk, and an apple, which he eats with his temporary "family." His "parents" even coax his "siblings" to share their brown sugar with him as a topping for his oatmeal.

Thanks to the generosity and quick thinking of the strangers in the food line, Bud is able to continue on his journey to find his father with a full stomach.