S1, E13: Alan worries that Charlie will become infected with Jake's contagious cold; however, Alan gets sick instead. Jake heals, and Charlie is fine. Desperate to get a date with a sexy woman, Charlie volunteers a very reluctant Alan to escort the woman's sister, turning the date into a foursome. Charlie tries to speed Alan's recuperation, but when Charlie gets ill and Alan discovers how attractive the sister is, their roles reverse. Meanwhile, Alan objects when Charlie takes advantage of having the same tastes in humor as his 10-year-old nephew.