Well, Mr. Oatmeal is apparently repeating an urban legend. I look at a wombat, and no way do I believe that thing can move at 25 mph (40 kph). I found a piece[0] which indicates this might have been some confusion as to metric vs imperial decades ago that was then retransmited through the ages.

[0] https://www.abc.net.au/news/science/2024-04-13/how-fast-can-...