Scenario: Aku separates Jack and Johnny and runs him through a gauntlet of every kind of manipulation and attack Aku has learned in his long, LONG existence. Doesn't work. Absentmindedly messes up Johnny's hair while on the verge of giving up and THAT gets a reaction. Aku then strives to give Johnny Bravo the worst hair day of his life to bring out his evil heritage. (he's got some competition considering the time with the chili, bugs, birds, cats, dogs, and giant ant)
YES OH MAN, I had an idea about Aku separating/tormenting them anyway, that’s a perfect reason for it to happen! And then Aku would probably throw them right back together as soon as Johnny is seeing red from the worst hair day in history.