It was a waste of time claiming he didn't have a clue as to what Draco was talking about. Blaise might not like that his friend knew about his odd attraction to the female Weasley's assets but he did. "Plan to keep the equipment attached, thanks. It might rot off as many blokes have been in that." Not to mention the witch might just decide to hex it off.
"I wasn't sure which of the catalysts you wanted," Blaise said pointing to the two vials. The book said one thing but Pepper-Up was more potent if you substituted. Slughorn didn't mind a little creativity. If Blaise could deliver a superior potion, he would. If only because it was always amusing to best Granger and see her knickers get in a twist.