The desert has only showed up twice before.
The first time was in comic #44, when Cyril was dreaming and/or has a flashback. The dream included (in order):
-Cyril finds himself in a desert -his parents come, saying they are leaving him there, and have adopted a zombie instead. -As the parents leave, one of them says that there are desert pythons (not in-game) and leaves.
The second time was the Mother's Day comic, in the second panel.