Generating crema with a moka pot? I have a stove top percolator for making espresso.  It does not generate any crema.  it possible to do so with a stove top percolator?
Moka pots (or stove top percolators) usually produce a pressure of around 1.5 bar, while most coffees require a pressure of at least around 6 bar for a crema to appear. However, there are some Moka pots with a special valve (called Cremator) which helps creating more pressures and thus produce a crema.

By the way, a real Espresso has to be brewed with a pressure of 9 bar ± 1, according to the Italian National Espresso Institute, so it can't be brewed with a Moka pot.