Chaff kisses Katniss as a joke. He wishes to mess with Katniss' image as "pure." Thus, he does not hesitate to kiss her when Haymitch introduces the two of them. Katniss is taken aback by his kiss and pushes him away. Although Chaff is a part of the rebel network, he is unable to win over Katniss' trust and is, therefore, not of much use to her in the arena.