An accidental president, the king of the oceans and a fair number of supervillains will meet thousands of Utah geeks, cosplayers and enthusiasts at the FanX Salt Lake Comic Convention in September.

The semiannual convention Tuesday announced 21 celebrities signed on to appear at this fall’s event, Sept. 5-7 at the Salt Palace Convention Center. And one of them, voice actor Jess Harnell, showed up in person to help make the announcement at the Megaplex at Jordan Commons.

Harnell, known for his work on “Transformers” movies and the “Animaniacs” TV series, called FanX “the best comic convention in the whole world,” drawing cheers from the dozens of costume-clad fans at the announcement.

Other actors Harnell works with “all talk about this con, and that they have to come back to this con,” Harnell said, adding, “if [they] don’t invite me formally, I will go to Target and buy a table and show up anyway.”

Harnell told the fans he will bring back one of the convention’s most popular events, Twisted Toonz, to the September event. In Twisted Toonz, Harnell and other voice actors gleefully massacre a popular movie script, performing the characters in different voices.

Dan Farr, the convention’s co-founder, backed up Harnell’s endorsement. “We’ve had a really solid reputation in the [convention] community,” Farr said. “I go to other conventions and they treat me like a guest.”

Tickets and passes for the September event are on sale at fanxsaltlake.com. Farr said the “loyalty launch” discount is in effect through Sunday, Father’s Day.

Here are the other celebrities announced Tuesday as coming to FanX:

• Keifer Sutherland, now playing President Tom Kirkman on “Designated Survivor”; also played counter-terrorist expert Jack Bauer on “24,” and appeared in “The Lost Boys,” “Young Guns” and other movies.

• Dolph Lundgren, who played King Nereus in “Aquaman,” and the Russian boxer Ivan Drago in “Rocky IV” and “Creed II.”

• Christina Ricci, who became famous playing Wednesday Addams in two “Addams Family” movies, and more recently played Lizzie Borden.

• Jason Patric, whose screen credits include “The Lost Boys,” “Sleepers” and “Speed 2: Cruise Control.”

• Matthew Lewis, who played Neville Longbottom in the “Harry Potter” films. (Previously announced.)

• Two villains from “The Flash”: Danielle Panabaker, who plays Killer Frost, and Carlos Valdes, who played Reverb.

• Two villains from “Once Upon a Time”: Lana Parrilla (Evil Queen) and Rebecca Mader (the Wicked Witch).

• Kel Mitchell, who starred in “Good Burger” and Nickelodeon’s “Kenan & Kel” (both with longtime comic partner Kenan Thompson).

• Sebastian Roché, who played Balthazar on “Supernatural” and appeared in “The Vampire Diaries” and “The Man in the High Castle.”

• Ryan Hurst, who played Opie on “Sons of Anarchy.”

• Lesley-Ann Brandt, who plays Mazikeen on “Lucifer.”

• Megan Follows, who played the title role in the 1980s “Anne of Green Gables” series, and played Catherine de Medici in “Reign.”

• Charles Martinet, who provides the voices for Mario and other Nintendo characters.

• Jonny Cruz, a voice actor for the video game “Overwatch.”

• Arryn Zech, Lindsay Jones and Kara Eberle, voice actors on the online animated series “RWBY.”