I love boiled wool German slippers and have worn them for years.  If not for the exceptionally stupid label RIGHT under the heel on both feet, these would have been five star slippers.  The label, however, is annoying, even through socks (thick winter socks, too!)  and is both sewn and glued in place so it can't be removed.  (I took a seam ripper to the label, thinking the irritation would be easily removed, but it's glued down with extremely zealous glue in addition to being sewn to the wool so there's no removing it without taking a divot of wool out, too.)

This is the stupidest place they could possibly put a label.  There's already one sewn on the side of the shoe.  They really should just put a sticker on the sole to mark the size instead of inserting this stupid, uncomfortable, very permanent label under both heels.  Not as annoying as a pebble in your shoe, but it would be so much better without it.