There was always something a bit dubious about the claim that Blue Beetle tied into James Gunn's DC Universe. The film was mostly through production before Gunn and co-CEO of DC Studios Peter Safran devised their overall plan. The reason this still works, however, is it widens this new DCU in very subtle ways. The Green Lantern "cameo" in the film's opening is one example of how Blue Beetle makes this new universe feel lived-in.
Source：https://www.cbr.com/blue-beetle-green-lantern-easter-egg/
