Comic books and fan fiction go hand-in-hand, and slash fiction is absolutely at the centre of this. Slash fiction is basically fan fiction that involves characters engaging in sexual relationships, and Deadpool is clearly a fan. Here, with him riding on Spider-Man's back, he mentions that fans will have a field day writing about the two heroes' sexual exploits. Spider-Man quite clearly doesn't get the reference, being less self-aware than his irritating companion.