"The Super Salesman" is a 1947 Heckle and Jeckle cartoon.
Heckle and Jeckle. the two talking-magpies are selling hair-tonic in a public park without a license. They are chased by the park caretaker whom they trick again and again. Then a stern police dog get involved and their feathers start to fly. They find a good use for the hair-tonic but it backfires on them. 
- The Super Salesman (1947) - Plot Summary - IMDb