 Ron learns in the third season finale , " Li 'l Sebastian , " that Leslie and Ben are secretly having an affair despite Chris ' ban on workplace romances , and he warns them they are risking a political scandal that could cost them their jobs . Later , at the funeral of Pawnee 's celebrity miniature horse Li 'l Sebastian , Ron is nearly killed as a result of Leslie and Ben 's affair . When their efforts to hide their relationship accidentally cause Li 'l Sebastian 's eternal flame to be filled with lighter fluid instead of propane , Ron creates a massive fireball when he lights it , which burns off his eyebrows and part of his mustache . The season ends as a horrified Ron learns that his first ex @-@ wife , Tammy , has arrived to see him ; the news is enough to make his second ex @-@ wife , also named Tammy , run away in horror . 
