When Eren is bored, either in a meeting or in general, he starts playing with Levi`s cravat. He finds it so fun to fluff it up and then press it down again, Levi never even notices anymore with how much he does it. He just carries on whatever he was saying or doing like there isn`t an adorable Eren attached to his cravat.
There was a time when Oluo thought he could try it, since the newbie got to, and wound up almost getting his wrist broken. Everyone agreed Eren was special and could probably get away with stabbing Levi if he wanted.