"Fly on your own. Find your way home."
How to Train Your Dragon: The Hidden World - Easter Eggs & Hidden Details
Easter Eggs
Toothless drawing in the sand
When courting the Light Fury, Toothless draws a picture of her in the sand. This directly mirrors the scene in the first film where Hiccup draws Toothless, symbolizing that the dragon has learned artistry and affection from his human.
Drago's Bewilderbeast
In the wide shots of the Hidden World, the massive Bewilderbeast from the second film (missing a tusk) can be seen in the background, confirming it retreated there after its defeat.
Book opening line
The film ends with the voiceover 'There were dragons when I was a boy,' which is the exact opening sentence of Cressida Cowell's first How to Train Your Dragon book.
Valka's Staff
The whistle mechanism in Valka's staff is used to communicate with dragons, a detail carried over from the second film that shows her deep, non-verbal connection to the species.