In the picnic sequence, whatever the planet in the background is is supposed to be is shown much, much too large.
It may be witchcraft of course but otherwise, Mars only has about a third of Earth's gravity.
It may be witchcraft of course but otherwise, Mars hardly has any atmosphere to speak of, and what extremely little gas is there, is mostly CO2. This also means there is no protection from either solar or cosmic radiation, especially since the planet has lost its magnetosphere.
Mars doesn't have snow.
Right before the lima beans fall both Caroline Rhea and Beth Brodrick flinch and wince right before they fall.