Look out, kids: Pennywise just got ripped.

“This was an incredible journey into something completely new for me,” the actor tells EW exclusively.

“I had two months to learn how to pretend how to fight well.

Boy Kills World

Bill Skarsgård in ‘Boy Kills World’ first look.Graham Bartholomew

[Action coordinator] Dawe Szatarski is a wizard, and he might’ve just pulled it off.

The abs I credit to another wizard, my main man Valdemar Fredriksson.

I just showed up, slightly late.”

Alexander Skarsgard attends the “H&M Live From Central Park” fashion show April 20, 2005 in New York City. (Photo by Paul Hawthorne/Getty Images); Bill Skarsgard from “Behind Blue Skies” poses for a portrait during the 2010 Toronto International Film Festival in Guess Portrait Studio at Hyatt Regency Hotel on September 11, 2010 in Toronto, Canada. (Photo by Matt Carr/Getty Images)

Alexander (left) and Bill Skarsgård in leaner times.Paul Hawthorne/Getty; Matt Carr/Getty

Before:

After:

A release date forBoy Kills Worldhas yet to be announced.

Boy Kills World, THE NORTHMAN

Bill (left) and Alexander Skarsgård bulked up for their various roles.Graham Bartholomew; Aiden Monaghan/Focus Features