April 11 is the 101st day of the year.
The Pinwheel Galaxy (also known as Messier 101 or NGC 5457) is the location of planet Uriel, the home of the angelic beings disguised as crazed witches in Madeleine L'Engle's A Wrinkle in Time.
In The Matrix, Neo's apartment number is 101.
In 1984, the torture room where you face your personal definition of "the worst thing in the world" is Room 101.
There are, of course, 101 dalmations in 101 Dalmations.