Killroy Was Here

In April 2014, Kevin Smith announced the Christmas-themed horror movie Anti-Claus, with a script based on the episode The Christmas Special of his Edumacation podcast.[9] The script was co-written by his Edumacation co-host Andrew McElfresh, marking it the first script Smith collaborated on with another writer. Filming was initially scheduled for September 2014, with Tusk (2014) actors Justin Long, Michael Parks, and Haley Joel Osment returning as cast.[9] The movie centered around the European folklore figure Krampus, a devil-esque creature who punishes naughty children.[10]

Principal photography began on June 15, 2017, in Sarasota, Florida,[11][12] shooting in areas around Ringling College of Art and Design and Nathan Benderson Park, before moving to Longboat Key.[13] The film is a horror anthology based on the graffiti phenomenon that Smith will direct,[14] based on a script co-written by him and Andrew McElfresh, marking the first time he will share writing credit on one of his movies.[15][16] The script is a retooling of their Anti-Claus movie, which was initially cancelled after the release of Krampus (2015) due to the similar story.[17]

In January 2018, Azita Ghanizada, Ryan O'Nan, Justin Kucsulain, Kathryn Parks, Brendan Ragen, Michael Perez, and Cindy De La Cruz were confirmed to be starring in the film,[7] while Andrew McElfresh, Tony Stopperan, Joe Restaino, Nick Morgulis, Jordan Monsanto, and Adam Yeremian signed on as producers.[18] In the same month, Smith's daughter, Harley Quinn Smith, joined the cast.[19] In August 2018, Chris Jericho was confirmed to be starring in the film,[20][21][22][23] before filming wrapped in October 2018.[24]

In April 2020, Smith revealed that the tone and style of Killroy Was Here were inspired by Creepshow (1982), another comedy horror anthology film.[25] Robert Kurtzman designed the titular character, describing it as a "long-nosed monster".[8]