Beetle and Sarge have a special relationship. Sarge's job is to get Beetle to do his duty as a soldier in the U.S. Army but Beetle constantly resists work in any form. As a result, they are in perpetual conflict. But they also need each other. Beetle's resistance has no meaning without Sarge's authority and Sarge has no purpose without someone to boss around.
The Sunday page above reveals this co-dependence. In many ways Sarge is like a parent to the men in his command. He has to keep them in line but at the same time he worries about their welfare. He reminds Beetle that it is time for him to go to bed. When Beetle acknowledges Sarge's concern, Sarge immediately starts acting tough again. This subtle back and forth is one of the most important dynamics in Beetle Bailey.
Mort Walker and his creative team have always been well aware of how this works. The drawing below, entitled "Friends Forever" was produced for a print series done by Abrams in 1978 and features a classic image of Beetle and Sarge showing affection for each other
– Brian Walker