Very convincing as a younger Tommy Lee Jones
Just saw MIB3 a couple of days ago. Josh Brolin's performance as a young Agent K is what stood out the most for me afterwards. He really became a believeable younger version of the character. It must have required a lot of practise and watching tapes to mimic mannerisms, speech, etc.
In fact, he kinda saved the movie for me as Tommy Lee Jones seemed pretty tired. But the banter between Brolin and Will Smith was great.
Can't believe I haven't seen him in anything else.