This is Dr. Jekyll and Mr. Hyde from Lego Minifigures Series 9. A must have for me primarily because he's a Victorian era Two-Face!
Also because he works perfectly in the Monster Fighter themed sets.
He comes with a vial of potion, or maybe grape juice.
This is a great minifigure even if he's not really any sort of official Jekyll/Hyde or Two-Face character. This is more of a 'mid transformation' design, and it's a shame the set didn't come with two heads, a normal Dr. head and a completely transformed Hyde head. But oh well, points to Lego for their attempt at least.