Mechanical buckling of a switch or button produces an attractive sensation of touch; however, a method to optimize the haptic pleasantness caused by buckling has not been established and well demonstrated. In this study, we optimized a popping elastic dome toy that provides pleasant haptic sensations when pushed or buckled. Toys with different physical parameters were manufactured following the Box-Behnken design, and their comfort was evaluated by the users. The design parameters that maximize haptic pleasantness were determined using the response surface method. The optimally designed popping toy was equally as comfortable as the best one in the initial specimen set. Further, haptic pleasantness was found to be largely determined by the ease of pushing and haptic feel at the moment of buckling. This approach is expected to improve the haptic sensations of various commercial products such as mechanical switches.