Peanuts by Charles Schulz for August 20, 1968
Transcript:
Snoopy sits on the doghouse. Charlie Brown holds an envelope out and says, "Here, Snoopy, you got a letter . . ."<BR><BR> Snoopy holds the envelope and thinks, "It's from Lila! Oh, no, not again! Why does she keep bugging me?"<BR><BR> Snoopy thinks, "That Lila! There was one thing she couldn't seem to learn . . ."<BR><BR> Snoopy frowns and thinks, "Never bug a beagle!"<BR><BR>
I thought it was “Never beg a bagel”.