In By Sidney Lumet (2015), Lumet reveals that most of Lloyd Bridges irate moments were improvised by the actor himself, who got carried away by the whole scenario of the story. Bridges got so emotional that he made use of some profanity that wasn't included in the script which worried the director a little since this was a live TV project.
Included in the Criterion edition of 12 Angry Men (1957), spine #591.