The big, big block in the Arthur/Merlin friendship is the status issue, that Merlin is the servant and Arthur is royalty, and in that time, princes did not socialize with their servants; that wasn't the done thing. It just so happens that their relationship, their friendship, is strong: they have been through the thick and the thin of it all.

Fighting in the name of freedom has too high a price," Merlin sighed as he leaned into his mother's arms.

If you could really see that tree over there," Merlin said, "you would be so astounded that you'd fall over.

"Said by Merlin

Merlin's beard.

How in the name of Merlin's pants have you managed to get your hands on those Horcrux books?

So why in the name of Merlin's saggy left -

But fate, as Merlin always taught us, is inexorable. Life is a jest of the Gods, Merlin liked to claim, and there is no justice. You must learn to laugh, he once told me, or else you'll just weep yourself to death.