Peanuts by Charles Schulz for August 19, 1952
Transcript:
An annoyed Snoopy sits on the grass in front of Charlie Brown. The latter holds a ball and says, "Here, Snoopy...catch!"<BR><BR> He throws the ball and a hits an unmoving Snoopy with a bonk atop his head.<BR><BR> Charlie Brown stands looking puzzled.<BR><BR> He stands behind Snoopy and says, "I'm sorry...I didn't know you were in a mood..."<BR><BR>
The only strip suggesting that Snoopy is female? :-p