First appearing in 1955’s Godzilla Raids Again, the monster has seen itself play both hero and villain to Godzilla’s presence throughout the classic eras of Toho Godzilla movies.
Again, the rights issues being what they are between Toho and Warner Bros, there may not have been clearance to use Anguirus as a full-fledged Titan in Godzilla: King of the Monsters.
And while it may not be able to jump into the fray just yet, the possibility of Michael Doughterty using him as just an easter egg is enough to lay the framework for a potential appearance down the line.