A gecko licks the morning dew off its eyeballs. The nocturnal reptiles collect water on their eyeballs in the early morning when a mist bank descends as cool coastal air hits warm desert air. Then they lick it off to have a drink.
I think the reason otters do that with people is because when they were babies they were able to be picked up and now that they're big they can't. Now when they see something bigger (also friendly) than them, it's an automatic instinct.