Do you add your own drum parts to songs?

Just wondering if I'm the only one that does this. Some times when I'm driving and listening to music I really like, usually stoner metal, I'll add in my own drum parts by hitting parts inside the car. I do not attempt to match what the drummer in the song is doing, I come up with my own part that works with the beat, kind of like I'm jamming with them. I also do bass lines sometimes.