Aku has been made of Mulan Mcnugget Sauce the whole time

Long ago in a distant land, I, Rick Sanchez, smartest man in all universes, unleashed an unspeakable April Fool's prank! But a foolish samurai warrior wielding a magic sword stepped forth to oppose me. Before the final blow was struck, I shot open a portal in time and flung him into the future, where my science is law! Now the fool seeks to return to the past, and undo the future that is Mulan McNugget sauce!