In the Season 5 episode " Last Cigarette Ever ," the HIMYM gang secretly struggles with smoking, ultimately sharing a rooftop cigarette they believe to be their last. While they all claim to have quit, the episode reveals through a future perspective that each character actually stops smoking at different times, with Marshall quitting in 2012, and the others quitting between 2010 and 2017. This episode, featuring the introduction of Robin's love interest Don, highlights the difficulty of breaking bad habits and highlights the characters' shared vices.