fungus-amungus
Explanation
This comic applies the real-world phenomenon of parasitic fungi that control insects to the beloved children's television character Cookie Monster from Sesame Street.
The scene shows several Sesame Street-style characters gathered around the body of Cookie Monster, who has died. A dark fungal growth is visibly sprouting from his spine. The characters react with shock:
"Oh my God, he's dead."
"There's fungus growing out of his spine."
"It must've been controlling him."
"No wonder he had to eat so many calories. Why didn't any of us realize it?"
The caption below reads: "It wasn't the fact of Cookie Monster's death that shook Sesame Street to its core, but the method of his demise."
The joke references cordyceps fungi (and similar parasitic organisms like Ophiocordyceps unilateralis), which are famous for infecting insects, taking over their nervous systems, and compelling them to behave in ways that benefit the fungus's reproduction -- for example, forcing ants to climb to high places before the fungus erupts from their bodies. This concept was also popularized by the video game and TV series "The Last of Us."
The humor comes from retroactively explaining Cookie Monster's famously obsessive, single-minded cookie consumption as not a personality trait but a symptom of parasitic fungal infection. His insatiable appetite ("C is for cookie, that's good enough for me") was actually the fungus demanding calories. The other characters' reaction -- "why didn't any of us realize it?" -- plays on how obvious this "explanation" seems in hindsight.