This is a common misconception. TST is not a joke or parody religion.

Also from their FAQ

IF YOU DO NOT BELIEVE IN THE SUPERNATURAL, HOW IS TST A RELIGION?

The idea that religion belongs to supernaturalists is ignorant, backward, and offensive. The metaphorical Satanic construct is no more arbitrary to us than are the deeply held beliefs that we actively advocate. Are we supposed to believe that those who pledge submission to an ethereal supernatural deity hold to their values more deeply than we? Are we supposed to concede that only the superstitious are rightful recipients of religious exemption and privilege? Satanism provides all that a religion should be without a compulsory attachment to untenable items of faith-based belief. It provides a narrative structure by which we contextualize our lives and works. It also provides a body of symbolism and religious practice — a sense of identity, culture, community, and shared values.

If you want to compare and contrast TST and the Church of Satan, there's an excellent in-depth article here.

Neither one worships Satan. They are both religions. However, their values are very different.