Jason Garcia poses as The Joker from Batman at the 2015 Comic-Con International in San Diego, California, July 9, 2015. (Photo by Sandy Huffaker/Reuters)

Attendees dressed as Poison Ivy and Harley Quinn arrive for opening day of the annual Comic-Con International in San Diego, California, United States July 21, 2016. (Photo by Mike Blake/Reuters)

Convention goers dressed as bright colored Wookiees, a fictional species from the US epic space opera franchise Star Wars, prepare for a group photo outside the Comic Con 2016 in San Diego, California, USA, 22 July 2016. The San Diego Comic Con 2016 runs from 21 until 24 July. (Photo by David Maung/EPA)

An attendee dressed as Junkrat from the game Overwatch poses for a picture during opening day of pop culture convention Comic Con International in San Diego, USA on Thursday, July 19, 2018. (Photo by Mike Blake/Reuters)

Friends outside the convention center during opening day of the annual Comic-Con International in San Diego, California, United States July 21, 2016. (Photo by WENN/SIPA Press)

Attendee Emily poses for a picture at 2017 Comic-Con International on July 20, 2017 in San Diego, California. (Photo by Mike Blake/Reuters)

Rachel Hollon of Los Angeles was body painted as Harley Quinn at Comic-Con International in San Diego, USA on Jule 20, 2017. (Photo by K.C. Alfred/San Diego Union-Tribune via ZUMA Press/Rex Features/Shutterstock)