Sebastian St. Clair is a minor character in BoJack Horseman.
He is a former department store chain owner and celebrity who runs several charities in Cordovia. He is constantly seen doing volunteer work with the Cordovian people. One of the recurring themes with him is that he wants Diane to document his goodwill in a book like she wrote for Bojack Horseman.
Despite his superficially good actions, it becomes obvious to Diane Nguyen that he is in Cordovia for the positive publicity and to boost his image in the United States and in actual fact, does not care about the Cordovian people at all and spends most of his time making various statues, paintings, and tributes to himself instead of focusing on the war-torn country.
He's very arrogant, and got jealous whenever Diane showed interest towards the Cordovian people over him. Mr. Peanutbutter was jealous of him a bit, not wanting Diane to go to Cordovia with a " rich handsome bachelor".