Yes, he gained weight, did specific exercises, shaved his head, and used make-up artists.
To shape-shift accordingly, Bale has said that he shaved his
head, bleached his eyebrows, and gained 40 pounds. (Co-star Carell
also said that Bale did specific exercises to thicken his neck.) This
January, Bale waved off any praise for the extreme
Yes, according to this MentalFloss article
THORNTON PUT CRUSHED GLASS INSIDE HIS SHOES.
It gave him Karl’s famous limp.
Also corroborated by Chron (An independent Austin, TX newspaper) in this article
It hurt to play Karl
Thornton told James Lipton on "Inside The Actor's Studio" that playing
Karl was physically painful. His face had to ...