in 1964, a buddy agreed to smuggle his pal out of East Berlin... in the back of his Isetta. No, there is no trunk, there is no luggage area... he customized his engine area, removed the fuel tank, spare tire, rerouted the exhaust, and made a space big enough!

And they show how it was done on the new Grand Tour, episode 5. 

this is how much space he had to fit in

By the time the Berlin Wall fell in 1991, a total of nine people were smuggled to freedom curtesy of a BMW Isetta.

He removed the air filter, the heating system, the spare tire and the standard 13-liter fuel tank and replaced it with a tiny 2-liter canister—just enough fuel to cross the border. 

He stripped out t 

In 2019, BMW commemorated this historical event by releasing a cinematic short film about the ordeal titled "The Small Escape."

https://www.pacificbmw.com/the-small-escape-smuggling-passengers-across-the-berlin-wall-in-a-bmw-isetta/