Explain SMBC — the wiki for Saturday Morning Breakfast Cereal

This comic riffs on the concept of messenger pigeons and camouflage. A character observes that messenger pigeons aren't extinct, then describes a technology that involves camouflaging messages so they blend in among people -- essentially making the messengers themselves invisible to ordinary observation.

The joke is that the technology amounts to outfitting human messengers with simple camouflage so they can avoid detection -- not a sophisticated digital encryption or stealth technology, but literally just having people blend into crowds. The punchline arrives when the observer says they'd love to see these camouflaged messengers, which is inherently contradictory -- if the camouflage works, they shouldn't be able to see them at all. The comic plays on the paradox of wanting to observe something whose entire purpose is to be unobservable.