Far, far into the future, pretty much the entire Milky Way has been colonised by humans. The thing is that now the Empire has fallen, the technology of FTL travel has been lost in most places. Those who still have it are too busy fighting a war amongst themselves to be concerned with far-flung outposts.
Evolution has continued differently on different planets. Humans have evolved to fit the local conditions.
On the planet Schmell, there is a mutation that causes the human inhabitants all to have enormous feet while retaining pretty ordinary human proportions in every other respect.
Typically a six-foot male would have feet that are 2 ft (0.6 meters) in length.
What evolutionary or other pressures could plausibly cause this phenomenon and prevent it from dying out?
People still walk 'normally'.
Their feet are roughly twice as wide as 'normal' feet as well as twice the length.
The planet has been terraformed and can be considered very similar to Earth in most respects.
With the fall of civilisation on Schmell, the people still have memories and artefacts of the past but they are reduced to a pre-industrial style of living.