Mark chooses April Fool's Day to ask Callie to take their relationship to the next level, but his romantic gesture is threatened when Callie's vengeful ex-boyfriend returns to win her back. Meanwhile, Leonard tries desperately to redeem a winning lottery ticket as Randall attempts to cut himself in on the prize.
When the country's biggest pop star ("Lady Hoo-Ha") goes zombie, millions of her devoted fans follow suit. When Mark befriends one of the new zombies, Randall is forced to deal with his jealousy issues.
Mark becomes a masked crimefighter after he's bitten by a rabid Bat-Boy. With the help of his loyal sidekick, Koala Man, Mark wages war against New York's criminals and their catlike leader.
In honor of Twayne's 10-year anniversary of running the D.O.I., Callie and the crew throw him a Roast. But when Mark's attempt at edgy humor goes too far, Twayne quits, leaving Mark in charge. Before his first day as boss is up, Mark makes a management mistake so catastrophic that it almost destroys New York City.