Mordecai and C.J decide to break up for a bit because CJ still thinks Mordecai loves Margaret, but its really because Mordecai is really bad at admitting his true feelings for C.J.

Does CJ dump Mordecai?

Mordecai and CJ officially break up. It is revealed that Rigby and Eileen have been secretly dating for a few months. This episode is also the last major appearance of CJ. This is the first marriage of a major character in the series.

Why did Margaret dump Mordecai?

Throughout Seasons 1-3, she served as Mordecais love interest where they kissed and dated in Season Four, but they broke up after Margaret left town for college in Steak Me Amadeus and they agreed to remain just friends after she has returned, and after a love triangle involving her, Mordecai, and CJ occurred.

What is wrong with POPs?

In Prank Callers, it is implied that Pops was once a (somewhat) more serious man, until Mordecai and Rigby (who had travelled back in time to the 80s) collided with his younger self, causing him apparent brain damage and turning him into the quirky character he is known as in the series.