Adventure Time Comic Issue #24

Princess Bubblegum and Marceline show up at Castle Lemongrab asking Lemongrab why hasn't he been taken over by the Gum, he screams that he is better than the Gum and that sweet and sour are natural enemies. Lemongrab's loud and obnoxious personality annoys Marceline and the two nearly come to blows until Princess Bubblegum calms the situation with a tea party.  Deciding to test Lemongrab theory on sweet and sour, Marceline and Princess Bubblegum go grab Jake from the Gum and throw him into Lemongrab. Lemon juice squirts out of his head and soaks onto the Gum and it recedes, curing Jake.

Lemongrab remarks that none of the Lemon Kids have juices because of "reasons." Princess Bubblegum deduces that Lemongrab has only has enough juice left to give a drop to everyone, meaning they'll need to some introduce the juice directly to gum stuck in everyone brain. But before Princess Bubblegum can enact her plan of giving impromptu brain surgery to everyone in the Candy Kingdom, Jake comes up with another plan.

Soaked in lemon juice and using his stretchy powers, Jake envelopes Lemongrab and covers the entire Gum affected area. He then has Lemon squeeze out the rest of his juice and using his powers to insert himself into everyone's head to apply the drop the gum on their brains, freeing everyone.

Later, after Bubblegum continues her story, explaining that the Gum had a desire to hug everyone around it and had apparently learned mind control at some point. After the Gum experiment failed, she repeated the experiment, except that time she greatly reduced the sweetness and it resulted in Lemongrab. As for the Gum, she receded back to where she was before, a nearly bottomless hole marked "Gum Kingdom" until she learns boundaries. Princess Bubblegum jests that despite all her preparations, her kingdom still needed to be saved by a boy and his dog as her gentle chuckle turns into crazed laughter.