Try this for a laugh. Turn off the ignition. Push and hold down the trip odometer reset button on the speedometer. Turn the ignition key to position one (first click) whilst still holding the reset button, may take a few attempts but as far I know it works on all E36s and some other BMWs.
You will now be treated to a very jolly show indeed. First the DME will display a few of it's internal registers in the mileometer LED space. Next all the gauges on the dash will cycle from zero to full scale deflection and back again whilst all the warning lights illuminate.
The registers displayed are
Vehicle identification number
Number for BMW internal use
Number of wheel rotations needed to make up one kilometer
Index of changes
Esmerelda's Pages ~ Z3ers.com