What is this light and sound LEGO brick? I have some sort of light and sound LEGO brick I obtained in an assortment of various brand's bricks. The piece has three black buttons which flash red lights and play different sounds when there are two AA batteries inside the piece. It is genuine LEGO because of the LEGO mark on the studs; however, I can't find a part number on it.
That is actually two parts 30351 Electric, Light &amp; Sound Rocket Engine and 30353 Battery Box Cover. That sound and light brick was made in 1999 and only ever came in two sets. 

If you look through the assortment you got you might find the Rocket Engine Nozzle that goes with it.


Image from Brick Instructions.