Guardians of the Galaxy and Deadpool have been a great show of Marvel and Fox's willingness to work together. Fox was willing to let Marvel have rights to Ego for Guardians and Marvel was willing to give Fox the rights to change the power of Mega Sonic Teenage Warhead in Deadpool. And while Deadpool is always ready to make references to random movies, Guardians of the Galaxy Vol. 2 actually almost made a reference to Deadpool!
It would have happened during the Stan Lee cameo, when he was talking about everything he's done. As we know, the movie they ended up referencing was Civil War, with Stan Lee mentioning he was once a Fed Ex man. Which itself has recently stirred some people up in the continuity world, because of the timeline. But according to director James Gunn during a Facebook Q&A, one of the possible references was when Stan Lee was a DJ at a strip club. This would have been a direct reference to Deadpool. During filming, Gunn shouted out multiple things for Stan Lee to say he's done while talking with the Watchers, one of which was the Deadpool cameo. This would have been huge, because it would have connected the two universes together in a very interesting way. Sadly, for reasons unknown to everyone, that take was not used. But it makes one wonder if in the future something could connect them.