The BMW Isetta was a quirky little microcar built by BMW from 1955 till 1962. I've only seen one in my life, but evidently the aficionados are quite adept at keeping these things running.
Today, we find a picture of an Isetta that has been extensively customized, and seems quite ready to deal with any problem that might occur.
Yeah that appears to be a Ma-Deuce mounted to that thing. I don't know where the gunner would stand. I found the photo on Brownell's Facebook page.