It fascinates me. The FF meeting The Beatles. Reed and Ben serving in WW2. Cap had to have been revived in the 21st century. Spider Man hanging out with the original SNL cast. Iron Man meeting Rhodey during Vietnam. The Avengers appearing on Letterman. I love that Marvel has not rebooted (I consider things like Siet Cong or whatever it's called to be minor fixes that dont alter continuity). I read a great blog that uses Marvel continuity to put forth the idea that young Franklin Richards has subconsciously affected the movement of time in 616. What stories do you recall that now, with the passage of real world time, could not have possibly happened in the Marvel universe as was presented at the time?