"The Bachelor Party Corrosion" (Season 9, Episode 3), aired on October 5, 2015, splits focus between a disastrous Mexican road trip in physicist Richard Feynman’s old van and a "mini-bachelorette" party where Amy rebels against her mother's restrictions. The episode features key moments such as the guys attempting to fix a flat with thermite and Penny confessing her elopement to her father, Keith Carradine. For more details, visit The Big Bang Theory Wiki .