-어도 means "even if, even when", so this says the funniness survives whatever you do to it. Three lines use 생각해도 웃김 "still funny thinking back on it", which is a stock on-screen caption for a callback joke. Four more use 봐도 웃기다 — 서로 눈만 봐도 웃긴데 "they crack up just meeting each other's eyes", 내가 봐도 웃긴 거야 "even I thought it was funny". 내가 봐도 in particular means "even by my own reckoning".