Snilly Snape/Lily head cannon.
After he was sorted into Slythrin house Severus Snape waited outside Professor Dumbledore's office for the whole of his first night at Hogwarts. Professor Dumbledore found him in the morning, curled in a ball outside the entrance of his office. The boy looked up as Dumbledore approached him and begged him to let him try the sorting hat on again. Dumbledore agreed and Snape prayed and begged the hat with all his will to be transferred to Gryffindor, to be transferred back to his precious Lily. The hat refused to let him change but still Snape begged. Suddenly there was a knock at the door of the office and in a whirl of red hair Lily Evans came running in. Without seeing Snape she ran straight to Dumbledore.
'Please.' She begged him. 'Let me try on the sorting hat again. I can't be a Gryffindor, I have to be Slythrin.'
Dumbledore looked at Lily his eyes twinkling in amusement.
'That's funny; this young man here was begging the hat to sort him into Gryffindor'
Dumbledore gestured in the direction of Snape who was standing over by his desk, the sorting hat still in his hands.
'Unfortunately.' He said to both of the new students 'The sorting hat has placed you both in separate houses. It is not influenced by what one wants, but how one behaves, or will behave. Now off you go, you shall be late for your lessons.'
Snape and Lily left the office together and walked dejectedly down the spiral stairs. It was not till they were about to enter the great hall that either spoke.
'I can't lose you Sev; I couldn't bear it if our houses separated us from each other.'
Snape stood there a minute trying to collect his thoughts and overcome his emotions. He didn't know what he would do if he and Lily were ever separated. Suddenly without pausing to think what he was doing he leaned forward and kissed Lily on the cheek. He blushed bright red and muttered.
'I can't lose you either Lils, Swear we will always be friends no matter what happens.'
Lily tackled him with a hug and kissed him back on the cheek making the boy blush ever deeper.
'I swear.' She whispered in his ear before skipping over to the Gryffindor table. Snape grinned after her and made his way to the Slythrin table where he started to make friends in his own house, safe in the knowledge he and Lily would always be together.