An army of 400 Hamadryas baboons fights beneath the scorching sun in Ethiopia; Japanese macaques have adapted to survive in cold northern temperatures.
Sandy begins cooking and cleaning obsessively, causing Charlie to warn Alan that his girlfriend is a "nester"; Sandy becomes a lunatic during Christmastime.
Charlie plans a romantic date for Mia, hoping to consummate their relationship; Alan takes full advantage of an opportunity when sultry Kandi shows up.
Charlie and Mia's lifestyles clash when Charlie is forced to conceal his drinking and smoking from her as she attempts to makeover his unhealthy habits.
Alan is elated to be dating a 22-year-old babe, but he doesn't want her attending Jake's birthday party; Jake mistakes Alan's "performance" pills for vitamins.
Charlie is annoyed to find that Kandi has been living in his house for some time without him knowing, but is even more distraught by his own sexual dry spell.
A former Navy pilot suffering from wartime trauma is forced to take the controls of an airliner when the cockpit crew is incapacitated with food poisoning.
Two hapless nerds learn the ins and outs of being popular after using a computer to create the ultimate woman, who helps them find their inner coolness.
A high school student decides to skip school for one last hurrah with his girlfriend and best friend, but his principal is determined to catch him in the act.