Yes, Mad Eye brought the potion. "From inside his cloak Moody now withdrew a flask of what looked like mud. There was no need for him to say another word; Harry understood the rest of the plan immediately."

That isn't my question though. I just thought it was an odd choice for Rowling to select 6 others to look like Harry versus Harry looking like someone who already has a twin. The way it was written was comical. I enjoyed it, but it was a more complex solution than a more simple way of keeping Harry safe - that's all.