Kylee Russell (Eliza) was pregnant whilst filming. This explains why Eliza is always sitting down via virtual tablet and started interning at Z-Corp.
SERIES TRADEMARK: As was done in the first two films, Addison punches Zed in the face.
The film's plot was hinted at the end of Zombies 2 (2020) when something dropped down into Seabrook from the sky that caused Addison's white hair to glow, which is to do do with her revealed origins in the film, though there's a different reason in the film itself for it turning blue.
SERIES TRADEMARK : Another rendition of "Someday", originally performed by Zed and Addison, only now performed by the cast.