Not a Kiss.

"It wasn't a kiss!" Merlin said.

Gaius passed another page on his book. "I never said it was."

"Well, no, but-" Merlin spluttered. "It wasn't! There was the... the... the..."

"Potion?" Gaius suggested.

"THAT!" Merlin cheered. "Arthur and I had this potion, see, and everything was very confussing and really, it seemed as if nothing made sense. And see, it really wasn't a- well, even if it looked like it, it really wasn't. A kiss, I mean. It was just the potion and. That's it."

"Of course," Gaius agreed, pleasantly enough and then, just as Merlin was sighing, mollified, he added: "Oh, Merlin?"

"Yes, Gaius?"

"It has been some time since my last experience, and of course these things are always changing, but..." he glanced at Merlin from over the top of his glasses. "But I am still distinctly certain that once there's tongue? It's a kiss."