*squeee!*
Merlin is crack. Crack I tell you! I can't get enough. Also, Merlin was never more adorable than in episode 1 of season 2 when he comes home after getting knocked out with that gas in the stables and falling face first in the horse poo.
Gaius: What's that on your face?
Merlin: Nothing.
Gaius: What's wrong?
Merlin: Nothing.
So freaking cute! You can watch it here, last two minutes of the clip. And then Gaius is all nice to him. I adore them.