Social robots are effective in influencing and motivating human behavior. To gain a deeper understanding of how the robot emotional non-verbal behaviors might shape the human perception of the interaction while providing recommendations, we conducted a between-subjects experimental study using a humanoid robot in a movie recommendation scenario. This experiment aims at evaluating whether an incoherent use of emotional behavior, with respect to the presented contents, may produce a sort of humorous effect that positively affect the user perception of the recommendation. We evaluated, using an off-the-shelf solution, engagement and emotions shown by the users. Our results showed that a robot incoherent behavior does not distract the user, but it increases his/her engagement producing a positive emotional response. Such a difference is significant in the case of female subjects and depends on the considered emotions.