The Green Bay Packers actually do their own singing. They did not learn their choreography until the night before filming.
The Green Bay Packers got the chance to appear in the film after offensive lineman David Bakhtiari sent a tweet to director Elizabeth Banks, telling her that they were big fans of the first Pitch Perfect (2012) film and would love to appear in a sequel.
Improvisation was very common on the set.
Pentatonix appeared as the Canadian group during the worlds.
Real acapella groups were used during filming, including Pentatonix (winners of The Sing-Off season 3) and Penn Masala (who have released 8 albums and sung for President Obama).
Kay Cannon: the writer of both films appears as a news reporter after Fat Amy (Rebel Wilson) flashes President Obama.