The Frog Prince… a la Snupin.
It took Remus nearly an hour to realise that "Ribbit" meant "Idiot fifth years", "Ribbet!" meant "I'm going to string the author of Fairy Tale Love Magic! up by her thumbs and let her rot", and "Ribbet–ribbet–ribbet" meant, "Damn it, take the bloody spell off!" It took another half an hour and the wrath of Madame Pince to get the book from the guilty students, but mere minutes to explain the spell to Severus.
Remus crossed to where Severus squatted on a chair, examining the windowsill with interest.
"You're sure you want me to lift the spell?" he asked, amusement and trepidation warring on his face.
"Ribbit," Severus said impatiently.
Remus leant forward, tipped Severus' chin up with one finger, and covered Severus' mouth with his own. After a long moment, he was surprised to discover that Severus was kissing him back–and there were hands tangled in his hair.
When he finally pulled back, breathless and flushed, Severus unfolded himself to his full height and strode vengefully to the door. As he was shutting it he nodded once, sharply. "Lupin."
It took nearly half a day before Remus could allow himself to believe that Severus had winked.