Nice chapter.
Really missing Tonks and Fleur, would be good to have a scene with them to show what they are up to.
The magic 8-ball part was funny, imagine what the twins would do with something like that.
The twins are in the seventh year not the sixth. They are two years ahead of the trio.
Idea for the Luck Potion, Harry was thinking in one of the past chapters that he would have to be lucky to get the Gryffindor chasers to help him fulfill his fantasies, what if while a little typsy on Gryffindor liquid courage he drank the wrong vile and got really lucky.
How about Harry suggesting to the twins a bad luck potion for pranking, since you wouldn't want it to be to strong it should be easier to make.
Who owns the Prophet anyway?
How can Sirius help out for hours when the Polyjuice is likely to wear off soon, I doubt Harry gave him alot of his hair.
For a moment I thought you were going to have harry polyjuice as Malfoy senior to go to the prophet, I was also wondering about the possiblity of having Sirius polyjuice as Malfoy Sr. and 'bribing' Fudge in a sting operation. maybe he could declare Sirius innocent.
Update soon.