Why does the author have Polyphemus stop the large ram Odysseus is hiding under and talk to the sheep? What effect does this have on the reader?

They stay in their ram-carriages until morning, when Polyphemus lets the rams pass through the entrance. Odysseus' ram, the leader, goes last, and Polyphemus asks why it is not in its customary leading position. I thought Odysseus was pretty clever.