Christian Bale as Dick "Dicky" Eklund: "After both Brad Pitt and Matt Damon dropped out due to scheduling conflicts, Wahlberg suggested Bale for the role after meeting the actor at a preschool their young daughters both attended.
Given Eklund's drug addiction, Bale had to lose weight, which he found easy as he previously went through the task of losing sixty-three pounds in 2003 for The Machinist.
Bale researched the part by taking notes on Eklund's mannerisms and recording conversations for the character's distinct Boston accent.
Director David O. Russell believed Bale's task involved far more than mimicry. "Dicky has a whole rhythm to him, a music. Christian had to understand how his mind works." Russell and Eklund were both impressed by Bale's dedication to staying in character throughout filming".
IMHO, Bale should take the Academy Award for Best Actor!