[Perry Winkle]

The only ones I've come up with for myself:

As an ultramarathon runner (however poor at that I am) I will suggest that you train for an ultramarathon no matter how fit you are. If you are training for your first 5k I will earnestly insist that if you train for another month or two you can run your first ultramarathon.

As a trail runner I am baffled that people run on roads as anything other than a means to get to the trailhead. A road marathon is almost incomprehensible, though I have run one out of a sense of perversity.

(My wife's friend is a pretty fast runner. She does half-marathons. Has never run trails. I convinced her to go run trails with my wife. The poor woman fell and got 11 stitches. Woops.)