Most Penguin Software (or Polarware) games contain a humorous little remark about Penguins on the back cover of their games. In this case it is "Penguins have yet to defy gravity."
Since this is some sort of a Penguin software "trademark" it is only featured on the Penguin software release of the game, not on other package variations from other companies.
According to the magazine Retro Gamer, the Apple II version sold about 8.000 copies in 1982. Add