Several days later, Sirius was sitting in Snape's library, reading a thick book on Occlumency; he had studied it every day so far since switching lives with Snape. It was heavy stuff, and it wasn't easy…but then, he knew what was at stake. How long had it taken Snape to become an Occlumens, anyway? How long would it take Sirius to become one?

Sirius's work was interrupted by someone shouting his name—in a voice he recognized as his own.

"Snape?" he said, looking towards the fire, where his own head was sitting.

"The very same," said Snape-as-Sirius, glaring. "Listen, I have something to ask you."

"I was studying Occlumency," Sirius-as-Snape told him, irritated. "You interrupted me."

"Ah! Not so easy, is it?" Snape looked triumphant. "Anyway, you can take a break for a moment. Come over here."

Sirius groaned exaggeratedly and sat down on the hearthrug. "FINE! What is it?"

"Well…ever since I've taken on your appearance, I was wondering something," said Snape. "What exactly is your job as Harry Potter's godfather?"

"My job?" said Sirius, confused.

"Yes! What does being a godfather entail? What do you do?"

"Oh," said Sirius, stretching his legs out in front of him. "Well…put it this way. Harry hasn't got a father anymore. But he has got me—or, well, he's got you."

"What do you mean by that?" said Snape, his eyebrows contracting.

"I mean that everything that was once James's responsibility is now mine," Sirius replied. "But I don't see it as a job. I'm happy to play that part in Harry's life. In fact, in many ways he's sort of like the son I never had."

"It's a bit too soon after lunch for me to vomit," said Snape, who truly was looking disgusted. "You know I hate kids!"

"Harry's not a little kid anymore," said Sirius.

"Well, teenagers are even worse!" Snape said back. "And now you're saying I have to be some kind of…substitute parent to one?"

"That's right," said Sirius, "and you knew what you were getting into when you switched lives with me. That's what your job as Harry's godfather is—to be there when he needs you, just like James would have been if he was alive. That's not such a tall order."

"Yes, it is!" Snape barked. "You may be blind to his flaws, Black, but I am not!"

"Fine!" Sirius snapped. "If you think looking after Harry is so hard, I can come right over there and we can switch back. Where do you keep the antidote?"

"I haven't got any antidote," Snape informed him testily.

"What do you mean you haven't got any antidote?!"

"Which word don't you understand?" Snape said coldly. "There is no antidote in that house. Why would there be? I was under the impression that we weren't changing back until Christmas."

"Whatever!" said Sirius. "Just make some antidote, then!"

"It doesn't work that way, Black," said Snape. "I don't have the ingredients on hand in that house, so you'd have to wait until you get to Hogwarts to make it, and even then, the antidote takes two months to brew."

"Aren't there any shops that sell it?"

"I invented this antidote," said Snape, "so I'm the only one who knows how to make it."

"So you mean we're stuck like this?!" Sirius cried, panicking.

"I'm afraid so," Snape told him calmly. "Term will start in a little over two weeks. I will give you instructions on how to make the potion then."

"Fine," Sirius groaned. "But anyway, Snape, you have to promise me that you can look after Harry, even if it kills you."

"Except it will kill me, probably," said Snape. "Did you know that he ordered his post owl to peck you? From what I have observed, he has an extremely short temper—he even yells at his two closest friends."

"Well, he's been through something very traumatic," said Sirius. "You should be a bit more sympathetic to him. You're supposed to be his godfather until Christmas, so you have to humor him. In fact, he needs you now more than ever. It's not hard for me to accept Harry's flaws because I realize that his flaws are a part of who he is, and I love him for who he is. Besides, he's never yelled at me."

"True." Snape frowned. "In fact, he's actually remarkably calm when I'm around—well, as you, that is…"

"Harry knows he can always come to me no matter what," said Sirius serenely.

"Uh-huh," said Snape, still frowning. "I guess I'll have to get used to that."

"But looking after Harry isn't nearly as hard as this Occlumency shit," Sirius grouched, gesturing towards the abandoned book on the chair.

"You'd better study it, or the Dark Lord will kill you," Snape replied. "Just some pointers—try not to make eye contact with him, because eye contact is often necessary for Legilimency. Try to empty your mind when you come to meetings—and third, you must try Narcissa Malfoy's chili dogs."

"Nice try, Snivellus," Sirius said angrily. "But Narcissa is my cousin, remember? I've had those chili dogs before—and I'd rather not spend three hours in the bathroom, thank you very much."

"Damn," Snape muttered.

"However…" Sirius suddenly grinned. "That's exactly the sort of prank I would try to play on you. Looks like you're already getting the hang of acting like me."

Snape paused, gave Sirius the weirdest look yet, and said wonderingly, "You don't know how weird it is for me to see myself grinning like that."