Above the noise of the river they could all hear, now, the steady slosh-slosh of another craft heading towards them.
"Someone's following us!" hissed Magrat.
Two pale glows appeared at the edge of the lamplight. Eventually they turned out to be the eyes of a small grey creature, vaguely froglike, paddling towards them on a log.
It reached the boat. Long clammy fingers grabbed the side, and a lugubrious face rose level with Nanny Ogg's.
"'ullo," it said. "It'sss my birthday."
All three of them stared at it for a while. Then Granny Weatherwax picked up an oar and hit it firmly over the head. There was a splash, and a distant cursing.
"Horrible little bugger," said Granny, as they rowed on. "Looked like a troublemaker to me."

(Witches Abroad, Terry Pratchett)