2014 German release comparison of available 4:3 and 16:9 aspect ratios.

A unique feature of these releases is that while all episodes are presented in the original 16:9 widescreen-format, there is also a menu option to reduce them to the 4:3 format in which they were first aired on TV. This is done by means of a black mask ("a side matte"), blocking both sides of the screen. In terms of DVD technology, it is another subpicture stream.

However, depending on your player capabilities, or when fast-forwarding episodes, it cannot be guaranteed that the 4:3 version is always visible.

From www.facebook.com/Malcolm.DVD