Tropic Thunder is a comedy about a group of actors trying to film a war movie about a rescue effort, but find they must actually must do a rescue much like in the film.
Although a comedic or at least a performance with comedic elements is not too rare in this particular category a completely absurd sort of comedic performance is uncommon, although this sort of performance gave Kevin Kline a deserved Oscar win. Robert Downey Jr. performance certainly is a strange one as he portrays 5 time academy award winner Kirk Lazarus who is portraying African American Sgt. Osiris being a devoted method actor he delves into the role by darkening his skin as well as staying in character at all times even after a death that certainly would put the production on hold.
Although this performance is rather complex in many ways by Robert Downey Jr. it also is rather simple in its intent. The only real point behind the whole character's setup is to be funny more than anything else. Downey most certainly does this through each facet of his character. From firstly his portrayal of Lazarus's portrayal of Sgt. Osiris which is a gruff no nonsense sounding somewhat like the leads in some blaxploitation films. What really makes Downey funny as Osiris is just how serious he is actually in the role. Although the idea of his character is absurd Downey never treats it as such.
Downey's dead seriousness with his character is hilarious as he says every single line no matter how stupid it may sound, or strange with the same deadpan conviction. As the point of view his character makes sense though as well as Lazarus is suppose to take every role as seriously as possible, and with as much dedication as possible so no matter what he is saying it should be with this certainty. Really this sort of seriousness is perfect for the character and frankly if he tried to clearly make every line funny and every tried to obviously poke fun at the portrayal it would not have worked. This performance works because Downey shows at all times Lazarus sees nothing funny at all about what he is doing.
Downey is though remains funny though even in his character's pivotal moment near the end of the film where he confronts his whole idea of being playing all sorts of dudes. Again Downey is funny as well as being effective becoming the Australian actor who reminds me of Mel Gibson circa The Road Warrior. He again makes the over dramatics of his transformation, as well as the transformation itself both believable and funny because Downey always stays absolutely committed and invested into the role. The whole role of Kirk Lazarus frankly could have been quite a big failure in a great number of ways luckily though Downey is up to the task. Everything Downey does only amplifies the effect of his roles and the roles of Kirk Lazarus because he plays this entirely comedic performance just as he would a dramatic one.