Is this Guardians of the Lost Code 3D (2010)...?
From Wikipedia:
Guardians of the Lost Code (Spanish: Brijes 3D) is a 2010 animated adventure film, created by Ricardo González Duprat, distributed by Videocine.
During a field trip to the history museum, the students Freddy, Atzi, and Kimo discover a giant stone disk called the Codex in the storage room they are exploring. Three of the brije within it, the deities Quetzalcoatl, Ra and Chu Jung, emerge and reveal to them that they are the three people chosen to restore the ancestral alliance between humans and brijes, an alliance that was fractured with the emergence of science and technology.
The brijes are magical animal spirits that have been in contact with human beings since the beginning of time. Every human had a brije; the human cared for his brije and vice versa. When the human turned 13, a human shaman taught both partners a bonding technique that allowed them to synchronize and transform into a warrior form, gaining extraordinary power allowing them to perform various acts of heroism. Unfortunately, with the birth of modern science and technology, this union was slowly severed as humans stopped believing in magic, leading to tragic results. The brije in the Codex created and sealed themselves within it to protect the knowledge of the warrior form bonding technique from the forces of darkness that seek it.
It's an animated movie about three kids who wander into a storeroom in a history museum and find an ancient stone disc, through which they come into contact with brijes, supernatural creatures they can 'synchronise' with to assume monstrous "warrior forms."
The protagonists are a boy named Freddy, another boy named Kimo, and a girl named Atzi; they're paired with brijes resembling a grasshopper, a chameleon, and a hummingbird, respectively.
The main antagonist is a wealthy, middle-aged man named Elmer who recruits three kids to work for him; a boy named Spikes, a girl named Muty, and another boy named Zejas. Elmer and these three kids all have brijes of their own.
At around the 42:13 mark, the three protagonists meet a baby emperor with a magical tattoo of a Chinese symbol on his heel, which means "friendship." The same symbol then imprints itself on the foreheads of the three protagonists, and the girl, Atzi, says:
I didn't want a tattoo until I was eighteen! What will they tell me at home?!
(The symbols disappear a few moments later, though.)
Around the 55:30 mark, there's a scene where the protagonists undergo a test of character that involves them falling and having to save themselves through the strength of their friendship with one another. We see the symbols that were on their foreheads reappear and glow, and three symbolic feathers are depicted as part of the test.
Finally, toward the end of the film, at around the 1:17:48 mark, the main antagonist, Elmer, injures Muty, and Spikes and Zejas subsequently team up with the protagonists to defeat him.
