
...caused by relative MOTION between
the source of the wave and the observer.
The Big Bang Theory Season 1, Episode 6

- The ladies?
- Perpetual Motion Squad...
The Big Bang Theory Season 1, Episode 13

- Or there are MOTION sensors involved.
- No, I meant...
The Big Bang Theory Season 1, Episode 4

Leonard moves the meeting not occur.
Second? None heard, the MOTION fails.
The Big Bang Theory Season 2, Episode 10

How about the Perpetual Motion Squad?
The Big Bang Theory Season 1, Episode 13