When faced with the following scenario:
A seat on the train or bus is unoccupied, but the man sitting next to it has his legs spread so far apart that actually sitting in it would either a) prove impossible, or b) result in half of your ass sticking out into the aisle, largely cancelling out the palliative benefit of sitting down in the first place.
The proper response:
“Excuse me, but could I impose on you to constrain what’s obviously your enormous cock so that I may sit here?”
Requesting complete strangers to temporarily behave like human beings is often awkward and can lead to open confrontation. By impressing upon them the pretense that you believe them to be well endowed, you will both preserve their ego and defuse what could potentially become a sticky situation. Note: it is important that you not sound sarcastic while saying this, though not as important as, say, watching infomercials or scooping cat litter.