The train wagon rented by the police for their party is number PT 1448. 1448 are the last four digits of the phone number for any police station in Denmark.
According to Yvonne, high society lives "in Gentofte, on the right side of Lyngbyvej". This was where director Erik Balling lived.
The money for the coup is stolen from the "29 November 1974 Corporation". This date was director Erik Balling's 50th birthday.
Henning Sprogøe, son of lead Ove Sprogøe portraying Egon Olsen, came up with the movie's title after reading his father's copy of the early script. It then had the working title "The Return of the Olsen Gang", but when he understood that the main plot involved trains, Henning instantly suggested to his father that the title ought to be "The Olsen Gang on the Track"; 'on the track' giving it a double meaning as both a railway reference and a Danish idiom for having a hunch about something, in this case another heist. Ove passed the suggestion on to the film's director, Erik Balling, that immediately changed the film's title accordingly. Later, Ove returned from a day of shooting the film and presented his son with a gift from Balling: A bottle of high end Scotch whisky accompanied with a note that read, "Thank you for that title, Henning. We should have thought of that ourselves". Henning Sprogøe later worked as AD on Olsen-banden går i krig (1978).
Prominent in the film is the so-called "Yellow Mansion", a cozy railway tower housing the two signalmen Brodersen and Godtfredsen, the tower then being in actual use by DSB Railways. In 2013, the (primarily East) German Olsen Gang fan club learned that the old tower was due to be demolished, and an internet movement sprang up to prevent its destruction. Teaming up with their Danish counterpart, the DSB first gave the two national fan clubs one year to find a solution, and they managed to raise a total budget of DKK 5,000,000 including sponsorship and volunteers to disassemble, transport and resurrect the tower at the Gedser Remise Railway Museum near Gedser harbor, giving the ferries landing from old East Germany full view of the tower. Or though the interior of the actual DSB tower when in use was never like shown in the film, the interior of the restored tower was recreated to closely match the original set built on Nordisk Film's sound stage in Valby, Copenhagen. When the restored tower opened to visitors in 2016, during its first year the Remise Museum tripled their annual number of guests.
Poul Reichhardt: While both are wearing party masks, CID Inspector Jensen (Axel Strøbye) has an unexpected encounter with the chief of police, a veiled cameo by veteran actor Poul Reichhardt that portrayed the bumbling CID chief in the first two installments of the Olsen Gang series; Suggesting that the CID officer suffering the first few exploits of the Olsen Gang before the introduction of Jensen to the series, has since advanced to the position of chief of police.