This was a friend of mines idea and I just went along with it...
When intruders break into the park's house, Rigby gets kidnapped by a few thugs. It's up for Mordecai and the rest of the park crew to save him.
And who mysteriously kidnapped the young raccoon out of his will and from Mordecai's life? Maybe somebody who looks at the raccoon as a love interest.
And could there possibly be some love intention between the two best friend?
Even if they never knew it could exist...
That is, if they see each other again.