"Their clothes looked like they had slept in them." How can you tell?

This.
There are wrinkles that imply a shirt has come out of the wash and not been sufficiently ironed. And there are wrinkles suggestive of normal wear. But, having, say, a long diagonal fold right across the front of a shirt or pants is a giveaway that you’ve laid down in those clothes and stayed in that position for a long time.

Thank you for saying that so much better than I would have. But I had the same thought as you did when Beck mentioned it.

OTOH, for a really worthwhile Walk of Shame night prior, your clothes may have spent the night under the coffee table, flipped onto a lamp, slept on by someone’s pets, etc. So not exactly pristine even if you didn’t sleep in them.

Pilgrims and pilgrimages are a thing today and apparently always have been. Before the Christian Camino route there was a Pagan Camino route of pilgrimage which was basically the same but continued to the coast. . It is common on the Camino de Santiago (way of St. James) to be automatically considered a pilgrim as opposed to a hiker, though both are possible and both are recognized. In Spain, it is common to treat a pilgrim as if they were Lord Jesus Himself, as they might be. So that pilgrimage is not only for the pilgrim theirself, but for those who live along ‘the way’.

My wife made me change my shirt for a funeral, saying I “just look rumpled…”
“Have you never met me? Turning any clothing ‘rumpled’ is my super power!”

There’s a movie called The Way, about one of the pilgrims who walks the Camino Santiago. Along the way, he befriends a gypsy, who tells him that the real Way doesn’t end at the Iglesia, but at the coast.

Does the guy have his Polo shirt on inside out and he doesn’t realize it? Does the woman have a little party dress on that looks like she had an accident in a sushi restaurant?

They slept in their clothes, some of the time.

Great that we have two totally different conversations going on simultaneously.

I’ll bet that Pilgrims on the Mayflower really looked unkempt after sleeping in their clothes the whole voyage.

Yes I’ve done that. It is a beautiful and meaningful journey past Santiago to Fisterra and/or Muxia and much of the Catholic parts of the pilgrimage fade away and it shows its pagan heritage more. Fisterra means end (Fis) of earth/land (terra). The pre-Christian route would be a journey as far as one could walk towards the setting sun which was considered the end of the land and thus the end of the world. Where one would typically burn one’s clothes and swim in the sea of death which is a symbol of death and rebirth before watching the setting sun over the ocean at one of those 2 places (Muxia or Fisterra).

It also features prominently in David Lodge’s novel Therapy.