Although Deadpool belongs to the Marvel comic universe, it is currently under the ownership of Fox, which is also the reason that fans, despite their strong desire, cannot see Deadpool interact with other characters in the Marvel universe (specifically the X-Men, as Fox still holds the rights to these characters).
A dedicated Marvel fan has found a way to splice together scenes from Deadpool to create a humorous moment where Deadpool could potentially appear in the midst of the ongoing battle between Spider-Man and Captain America. You can follow this amusing interaction in the clip below.
Deadpool appears in the battle between Spider-Man and Captain America
