Follow Tiddalick and taunt him until he begins ranting. He'll drink a river and move a room. Keep taunting him until he continues to drink all of the water from the rivers (I counted 4). I'm not sure if it's timed, or randomly off of taunts, but keep taunting him every so often if he seems to stop. After the 4th river, he'll turn into a frog. Tickle frog, he laughs and expels the water back into the rivers, and runs away embarrassed.
You get the whois, and xp.