You can probably tell from the look on Merlin's face that he knew he shouldn't have ran off with Harold the Hedgehog!  Usually Harold sits in the hall and serves as a doorstop but Merlin has taken a liking to him and whenever he gets into the hall he makes a direct line for him and runs off with him in his mouth.  We've now found Harold a new home so that he is safe from Merlin (for the time being!).