Ducati Cucciolo, the first Ducati motorcycle, was actually a motorized bicycle with a 4-stroke clip-on engine. The bike became available just after World War II.
During the war, Aldo Farinelli, a lawyer and entrepreneur from Turin, worked with a small firm (Siata, short from Societa Italiana per Applicazioni Tecniche Auto-Aviatorie) to develop a small engine for mounting on bicycles. The first working prototype of this engine was ready in 1944 and earned the name Cucciolo (little puppy) because of the yapping sound its exhaust pipe made.
The Cucciolo engine, 48 cc giving 180 miles per gallon, became a hot seller—the manufacturer couldn’t meet the demand. So, Siata partnered with Ducati, which was a well-known manufacturer of electronics and appliances at the time. In 1947, Ducati received an exclusive right for the production of the engine. In 1952, after 200,000 engine units sold, Ducati offered its own complete vehicle with the same first 48 cc Cucciolo engine—that was the first Ducati motorcycle (vehicle if you like). The bike weighted 98 lb and had a top speed of 40 mph giving just under 200 mpg. The name Cucciolo was dropped in later models.
About the photos: It’s hard to determine which photo shows for certain that first Ducati model. I guess that the first model is the one on the first photo in this article because the bike looks more like a motorized bicycle and has a smaller tank. Image courtesy of Piero on Wikimedia Commons for his 1950 Ducati Cucciolo photo. (The first image has an unknown author).
About the video: The video shows a Ducati Cucciolo (Ducati T50) with a 4-stroke 48 cc engine and a frame manufactured by Quick in Olhão (Portugal) in 1954.