[citation needed] Four months into the eight-month program, Smith decided to drop out, but not before making a deal with Mosier: each would start writing a script of his own, and the one who finished last would help the other with his film.
[citation needed] He also contributed by appearing on-screen as multiple characters, including the angry hockey player and Willam Black (Snowball).
On 1995 film Mallrats, Mosier worked in organizing the budget along with line producer Laura Greenlee, while presiding over a much larger crew.
[citation needed] Mosier appears in the beginning of the film as the comics convention patron who gets into an argument with Banky Edwards (Jason Lee) after demeaning his career as a “tracer”.
In the film, Mosier played the assistant director on the set of the fictional sequel to Good Will Hunting and reprises his Willam Black character from Clerks.
The editing was also difficult due to the studio's desire to cut a large amount of Jennifer Lopez footage with Ben Affleck following the poor box-office performance of Gigli.
Mosier makes a brief cameo as a concerned father who shields his daughter's eyes from the sight of a character sitting on a toilet.
204 and episode 5 of the Comic Book Men podcast "Secret Stash") in which he and Smith interview Joe Casey; Mosier has written six scripts for the series.
[6][7] Mosier made his directorial debut with Illumination Entertainment's animated feature The Grinch, based on the book by Dr. Seuss, and co-directed with Yarrow Cheney.