Here in Germany we had a few cases where persons worked as hospital doctors for a few years without a license or diploma or even any medical training. They usually submitted a fake license to the hospital. There was a spectacular case in the 1990s where a former postal employee named himself "Dr. med. Dr. phil. Clemens Bartholdy" and later worked as a senior physician in a psychiatric hospital, also giving lectures [0]
> By chance, a co-worker recognised him on July 10, 1997, forcing him to go into hiding. At that time, an appointment was already set for an interview with Hans Geisler, then Saxony's Minister of State for social affairs, health and family, on the occasion of Postel's appointment to a professorship and to the position of chief of medicine at Saxony's hospital for psychiatry and neurology at Arnsdorf near Dresden.
In another case, a former barber worked for 20 years as a doctor, eventually becoming chief physician in a children's hospital [1].
Back in the 2000s there was a case of a medical student who failed her final exams 3 times, and instead of leaving university as she had to, she just continued her studies without the possibility to take any exams. After a few years, she printed a fake license and a fake diploma and secured a job as an assistance doctor in the children's hospital of the Hamburg University Hospital, eventually becoming a respected colleague (she was, after all, actually trained to be a doctor). After a few years, she failed to hand in the original license and her fraud came to light [2].
Last year, a fake anesthesiologist was uncovered in Fritzlar. She had no formal training and had handed in a fake diploma to get the job [3]. No one noticed until last year, at which time she had already accidentally killed 4 people.
Given that there are several such cases each year, chances are very high that there are still some fake doctors practising here.
We also had the famous Captain of Köpenick [4], an ex-convict who in 1906 put on a uniform, rounded up a few soliders, occupied a city hall in Berlin, arrested several employees, had them transported to the main Berlin police station for interrogation, ordered to block all local telephone calls for an hour, confiscated 4000 marks and disappeared. It took 10 days to arrest him.
[0] https://en.wikipedia.org/wiki/Gert_Postel
[1] https://www.aerztezeitung.de/Panorama/Hochstapler-im-weissen...
[2] https://www.welt.de/welt_print/article1142757/Falsche-Kinder...
[3] https://www.fr.de/hessen/hessen-drei-falsche-aerzte-einem-ja...
[4] https://en.wikipedia.org/wiki/Wilhelm_Voigt