Sitting in Potions (he'd arranged to have Potions with the Doctor and Sarah, mostly because the teachers figured he could keep an eye on them. They may not have blown up the dungeons, that honor went to his fellow Hufflepuff, Ace, but the pair could cause more than enough trouble if they wanted to. He should know, he'd been dragged into many of their shenanigans.) Harry watches Sarah and the Doctor argue while he pretends to look over his textbook.
Sensing a break in what ever their argument is about (potions isn't particularly his strong point), he asks. "Am I going to have to do some world class explaining later?" Because he would like to know if he's going to have to explain the latest bit of trouble to the headboy, Alistair. Or as most call him, the Brig or Brigadier, because he can have quite a military bearing.
"Harry." The Doctor gives him a wide eyed stare (his face cannot be natural…)
"Yes Doctor?"
"What the Brigadier doesn't know won't hurt him."
"Do I even want to know what you two have been planning in between the lines of your argument?" Harry asks with a sigh, sometimes he wonders if those two are long lost siblings or something.
"I'll tell you later Harry." Sarah replies, earning an annoyed look from the Doctor. To which she responds by sticking her tongue out at him.
"Very mature Sarah." Harry smiles, Sarah is adorable when she's being immature. As she's about to answer, the Doctor's cauldron starts smoking.
"ITS WORKING!" The Doctor exclaims, his voice echoing in the class room. Sarah and Harry share a "here we go again" look and pull out their wands. Who knows what his latest potions experiment will do…