Guardians Of The Galaxy Vol 2: 25 WTF Moments
14. "That Time I Was A Delivery Man"
Stan Lee's cameo in Vol 2 is pretty much the most important one we've seen so far, because of how it feeds into the long-standing fan theory that he is one of The Watchers (Uata, Earth's Watcher to be precise). Him conversing with the Watchers and seemingly telling them about all of his "past lives" throughout the MCU basically confirms that he's one character who keeps turning up in different roles.
It's a great touch, but there's a problem in the dialogue he's actually saying when we see him. He alludes to the time he was a delivery man, suggesting it was a past event.
The problem there is that that cameo happened in Civil War, which was set in 2016, and Guardians Vol 2 is set in 2014. So he hasn't actually been a delivery driver yet by this point.