Who does Pete ask if he's seen a guy that he can't see?
Donald Duck is doing some camouflage painting on a cannon with yellow, green, and red stripes and black dots (based on the colors of the Flag of Lithuania with bullet holes in it). Sergeant Pete sees it and scolds Donald, explaining that it needs to painted so it can't be seen.  Pete then demands that Donald re-paint the cannon to make it "hard to see".  Obliging to the sergeant's orders, Donald walks to the "Experimental Laboratory: Camouflage Corps", disregarding the 'keep out' sign, and walks in. He finds some "invisible paint", which he tests with his finger, and uses it to paint the cannon.
When Pete returns, he is shocked to find the cannon seemingly gone, believing it to be stolen.  But of course it isn't stolen, as the sergeant finds out the hard way by bonking his head on the underside of the cannon and discovering Donald inside.  Angered that Donald painted the cannon too invisible to see, Pete blows hard into one end of the barrel, sending Donald out the other end and into the bucket of invisible paint.  When Donald runs away, Pete finds out Donald has become invisible after seeing Donald's footprints on the ground.  Donald then swims across a lake, but the invisible paint doesn't come off.
Pete continues to chase Donald through a field of flowers, until he accidentally throws some of the flowers on Donald, revealing his outline.  Pete spots Donald and tries to catch him, but he gets away again.  However, this gives Pete an idea to find Donald.  When the General drives up, Pete's antics, including jumping around a tree while singing "Here We Go Round The Mulberry Bush" and throwing flowers, convinces the General that he is acting odd, especially after he asks the General "did you see a little guy that you can't see?"  The invisible Donald then puts a cactus down Pete's pants, making him scream in pain and jump around like a madman, making the General wonder what is going on with Pete.
General