It was a normal day around the castle, all the knights, including Merlin, knew Arthur and Gwen had a thing for eachother. So when they stumbled upon Arthur and Gwen conversing, the awkwardness between them was tangible, the knights and Merlin watched from afar.
Merlin, being himself, started to hum the first notes of Kiss The Girl from The Little Mermaid. Magical instrument appeared and started playing the song. Gwaine soon caught on and started to sing the lyrics when they started with Merlin singing along also. The other knights looking over at the two, before one by one, they all were singing.
Arthur could probably hear them if he was a day's ride away. He turned to them, burning their skulls with a death glare. Gwen, now stood next to Arthur, turned beet red from embarrassment. When the singing finished, the knights ran for their lives. So did Merlin, knowing he was going to have a long rough day at work tomorrow.