“Elementary My Dear Stacy” is the second half of the 4th episode of the 2nd season of the American television series Phineas and Ferb. It originally aired on Disney Channel in United States on May 15, 2009. It was written by Jon Colton Barry, and directed by Zac Moncrief. While in London, Candace and Stacy emulate Sherlock Holmes and Dr. Watson, while trying to bust Phineas and Ferb. Meanwhile, Perry must team up with British agent Double-0 0 in order to stop Dr. Doofenshmirtz from moving Big Ben to the Tri-State Area.