I posted this comment on Leaky, but I`ll post it here. (:

Wait, I just looked at the other picture of Harry & Slughorn. And Slughorn is wearing the same outfit – just without the robes. I’m thinking that that is the part where Harry asks for the memory, and this new one is where Harry wins Felix Felicis.

So, I`m thinking that Harry is going to get F.F. during class, and then that night he’s going to go as Slughorn for the memory. =) Make sense?!