Edward G. Robinson did not receive an Oscar nomination for portraying "Little" John T. Sarto also known as the titular Brother Orchid.
Edward G. Robinson was no stranger to playing gangsters as he originally made his name through Little Caesar. Little Sarto is a lot like Caesar, if Caesar lasted a bit longer, and lived in a nicer world to begin with. The early scenes of the film are quite interesting to basically watch Robinson play the part of Little Caesar but in a comedy. What's so great is that Robinson does not take this as an excuse to not take things seriously. Robinson isn't far off from the way he handled Caesar, other than there is just a strong innate likability he brings to Little Sarto to begin. Caesar always seemed a bit unpleasant, that's not the case for Sarto. Robinson still though would be convincing with the same performance even in a more serious minded film, as he still carries himself with the command and certain menace that he brings so effortlessly with his presence. Robinson manages to use this for the purposes of comedy quite effectively since he ends up playing everything in such a surprisingly straight fashion.
Robinson does not change his manner much that's what makes it so much fun to watch Robinson being basically Little Caesar though doing some things that are exactly fitting to Little Caesar. Little Sarto isn't really that different of a guy but in the early scenes of the film he's far more interested in where's he's going to be spending his retirement while having a very relaxed approach towards the life of the gangster. It's a great deal of fun just to watch Robinson do some pretty unassuming and non-threatening actions while still performing it as if he really was a big time mobster. There is actually really a surprising sweetness to this behavior that Robinson realizes as though Little Sarto is almost playing gangster, since he does not really have that edge that would require one to be a true mob boss. Robinson quietly shows that even though he's able to exude that tough exterior deep down he's a big softie. This is what Sarto unfortunately discovers when he attempts to reclaim his place as top dog, as his original second in command Jack (Humphrey Bogart) is not too keen on giving up what he got from Sarto's abrupt departure.
This leads to a gunfight which leaves a severely wounded Sarto who only finds refuge at a monastery full of monks. Here is where Robinson alters his performance slightly, but he does it so delicately that it absolutely works. What Robinson changes that he does start more directly going for laughs, although he was certainly getting them beforehand when not trying to do so. This is not a bad thing at all though as Robinson acts as the comic foil against the extreme straight men that are the monks played in a very calm and stoic manner. Robinson is hilarious though as he makes the gangster attitude and mannerisms all become a bit thicker as to accentuate the way Sarto just does not fit in, even after he decides to join the monks, in order to just use the place as a hide out while he plans his comeback. The way Robinson is just so off and out of place with the rest works in creating a series of funny moments. I particularly enjoy the way Robinson so quickly sounds off constant gangster speak that plays so well off against the monks who speak in a very straight forward fashion.
During his time with the brothers though Robinson does have some slight and momentary reactions that are very effective in suggesting that perhaps Sarto's beginning to see the place as a bit more than just a way for him to avoid his pursuers. Nevertheless Sarto decides to cut corners in his duties as the new novice brother, brother Orchid, by stealing milk as well as hiring a local boy to do some of his chores for him. This is eventually found out by a senior brother which leads him to announce this shame in front of the whole monastery. The moment is surprisingly heartfelt due to Robinson makes Brother Orchid's breakdown so genuine as he reveals how much he has enjoyed his time in the monastery revealing a stronger pride in his life than he ever did as a gangster. This whole setup could have fallen very flat. Robinson not only manages to make it believable that Sarto could transform himself into Brother Orchid, but also that he makes this transformation and realization as heartwarming as it is. This is wonderful work by Robinson as he turns his usual image on his head, to give a delightful performance.