Explain SMBC — the wiki for Saturday Morning Breakfast Cereal

This single-panel comic is part of a recurring "Grandfathering Fun Tips" series, which offers humorous advice on how to be an entertaining (or annoying) grandfather. The tip here is that the more anachronistic -- that is, absurdly outdated and historically impossible -- your complaints are, the better.

The grandfather demonstrates this by telling his grandson that "in my day, the cameras for your colonoscopy were hand-cranked." This is funny because colonoscopy cameras are a relatively modern medical technology, and hand-cranked cameras belong to the very early era of filmmaking. The joke combines the classic "back in my day" old-person complaint with a deliberately impossible historical claim, creating a mental image that is both absurd and mildly disturbing.