The celebration of Pi is celebrated in pop culture (both on Pi Day and throughout the year) more than any other mathematical construct. Many schools in the United States observe Pi Day, and its digital representation are often used by self-described "math geeks" for inside jokes among mathematically and technologically minded groups. In the Doctor Who episode "Midnight," the Doctor encounters the Midnight Entity that takes over the body of various characters. The character Sky Silvestry, when taken over, mimics the speech patterns of The Doctor by repeating, in synchronism, the square root of π to 30 decimal places. This involved the actors David Tennant and Leslie Sharp learning the sequence to be able to repeat it.
For more information on Pi Day and the many ways that it can be celebrated (plus lots of cool Pi mugs and t-shirts), please visit PiDay.org.
Yay for learning!