Heathcliff, using a giant reverse-whistle, summons some Ents (off screen) to rain leaves down on a neighbor who is unfortunate enough to not like the idea of living next door to a cat who can summon Ents.

Surprisingly, there are more than two humans in the strip in a seeming effort to prove yesterday's Heathcliff Paradox incorrect, but seeing as they're part of the same family and presumably take the same drugs, I'm willing to guess that they're having the same hallucination.