Arkady and Bazarov run into Sitnikov in town when they are visiting Matvei Ilyich Kolyazin. Sitnikov is an acquaintance of Bazarov's and announces to Arkady that he is not only a friend, but a "disciple" (12.27). Sitnikov insists on taking them to Madame Kukshin's, a woman he falsely believes will impress Bazarov.
Though Bazarov himself is a serious character, it's possible to read Sitnikov as a parody of the younger generation. At Madame Kukshin's, the narrator tells us "To Sitnikov the chance to be scathing and express contempt was the most agreeable of sensations" (13.44). He comes across as a fool whose self-conceit is paper-thin, and Bazarov treats him accordingly.
Sitnikov appears later – uninvited – at the home of the Odintsovs. He is insulted the next day when Bazarov and Arkady announce that they will be leaving. The situation becomes awkward when he insists on giving Arkady a ride in his carriage. When Arkady turns him down, Sitnikov goes back to Madame Kukshin's to complain about the two arrogant young men.
At the end of the novel, we learn that he has continued in his stupid ways, "his father sends him here, there, and everywhere as before, and his wife regards him as a fool" (28.11).