Using the neutral instead of the earth to supply electrons
Actually you do not need to connect the bottom of the Van De Graaff generator to ground.  But you will need to complete the circuit from the top ball to the bottom in order to get fun sparks.

For example if you use a soup ladle to get a nice spark from the top then the handle of the ladle should be connected to the bottom.

A very convenient sort of conductor to use for connecting the bottom to experiments is a ball-chain.  You would never use a ball-chain as a wire for low voltage but it works very nicely for high voltages.



Have Fun!