Twayne quits after getting roasted at his DOI 10-year anniversary party, leaving Mark in charge. Consequently, Mark almost destroys New York City.
When a Lilliputian arsonist escapes custody and hides in Twayne's nose, a miniaturized Leonard, Grimes and Mark enter Twayne's body to bring the fire starter to justice.
After Callie reveals she's been sleeping with other guys, Mark hooks up with an old college girlfriend to put his "open relationship" to the test. Jenny Slate guest stars.
Twayne throws a cruise ship party, and Mark Lilly is the only one who can save his friend Randall from a horrific plant species infection.