"No, I had my mummy do it for me," he snapped, and immediately felt guilty. He didn't know why, but it didn't seem right to get so snarky with Lupin. He'd never been outright rude or had played pranks on him... but he didn't stop any of it, either. Severus felt his lip curling at the memories before he forced himself to calm down, just standing aside to let his partner continue. After a moment of silence, he tried a different angle, testing out the waters.
"...you're welcome. Just, well, don't ruin this. My week's been less than stellar and I need something to go right." Severus was shocked at himself for saying those words. He didn't intend to be blathering his problems to the bloody werewolf during a Potions less, although he didn't quite hate himself for it. He shot a warning glance at Lupin, silently telling him not to make too much of this or he'd get testier than he already was.