Disclaimer; All the rights go to this one special lady, JK Rowling.
No Sexual Activity at Meals
Sirius Black and his boyfriend, Remus Lupin, were eating dinner with their fellow marauders James Potter and Peter Pettigrew in their fifth year. This wouldn't look a spot out of place if Remus' face wasn't getting redder as the meal progressed.
If you were the world's best observer, you would notice that Sirius Black was eating with his right hand under the table. If you were Remus, you would know that wicked grin of his meant no good business.
Dumbledore stood up regally to make an announcement. "There is a new rule in Hogwarts to be followed." Remus' breathing grew deeper and a low growl grew in his throat as Sirius' hand went faster.
"There shall be no sexual activity at meals." The room was silent, but Sirius was still as it, grounding Moony's prick into his palm.
"And that means you, Mr. Black," said, staring strait at the pair. He tried not to laugh as Remus went from red to green faster then a stop light. Sirius rocketed his hand from under the table as if burned.
"Thank you." He sat back down, which brought on the babble of conversation. Peter and James looked at Padfoot and Moony as if they had just grown extra heads.
The hall was letting out for the meal and Remus pulled Sirius into the first closet they could find. Just as Padfoot could light his wand, Moony had attacked his lips in a powerful kiss.
Sirius ran his tongue over Remus' bottom lip, then parted them. The smaller boy allowed this submissively, letting Sirius explore his mouth.
After a few minutes of face sucking, Sirius withdrew. "Let's finish this in the dorm," he growled into Moony's ear. The auburn haired boy couldn't nod fast enough.
And before you could say "No sexual activity at meals" they were in Sirius' bed, curtains drawn, with an epic silencing charm.