DMX made a surprise appearance at Alicia Keys' concert at Madison Square Garden in New York City last night (April 11).

Why is this important?

Because Keys' husband Swizz Beats -- a star in his own right these days -- started his career as a producer for DMX and the Ruff Ryders. They had a little reunion on stage. Very cool.

Watch the video and reminisce on when the dog ran rap.

Watch "DMX Surprises Alicia Keys at MSG" Video

Watch DMX's "Ruff Ryders' Anthem" Video