Explain SMBC — the wiki for Saturday Morning Breakfast Cereal

The comic tells the story of a man whose cat is dying. Learning his cat has a terminal condition, he decides to give the cat the ultimate feline bucket list experience. He tosses the cat into a ball pit of small flightless birds (a cat's dream prey), arranges for the cat to mate with a tigress at a zoo (fulfilling a "domesticated cat's sexual fantasy"), and even lets the cat finally "catch" a laser pointer by placing a red ball of fluff at the end of the laser's path.

When the cat eventually dies, the man has a seemingly profound realization: since the cat had no sense of its own mortality or existence, it was essentially "in heaven all along" -- living a life of pure hedonistic pleasure without the existential dread that plagues humans. The joke then undercuts this touching philosophical moment with the punchline that, since the cat had no sense of its own existence, the man figures the cat also won't mind being unceremoniously dumped in a dumpster rather than given a proper burial. The comic plays on the contrast between sentimentalizing pets and the pragmatic (if darkly humorous) implications of animals truly lacking self-awareness.