Knight's Quest 
You descend into a valley and come to a river.  After walking a short distance, you see a bridge.  You walk up to the bridge, but just as you are about to cross, you hear a crunching noise from underneath. 

"Hold on now!" a gravelly voice growls.  "What do you think you're doing?" 

Out from under the bridge emerges a hairy manlike creature.  He is nine feet tall, very fat and very ugly.  He is eating a box of graham crackers (contents:  100% bones of people named Graham).  The monstrous creature puts down the book he was reading (Harry Potter and the Troll That Stomped Him) and blocks your path onto the bridge. 

"This is a troll bridge," he says.  "You must pay the troll in order to cross." 

"You mean, it's a toll bridge," you say. 

"No, I'm a troll," he says.  "And this is my bridge, so it's a troll bridge, and you have to pay the troll -- and that's me." 

"I spent my last farthing on a Sanguinity Meal," you reply.  "I can't pay." 

"Well, then you'll have to answer the riddle." 

He draws in a huge breath. 

"What [he begins] walks on four legs in the morning, two legs in the afternoon, and three legs in the evening?" 

"A man," you reply. 

"Something other than a man?" you guess.