There are roughly 150 Spix's Macaws that make up the giant "2" of the U.S. teaser poster. The number of Spix's Macaws within that formation seems to loosely follow the real-life population of the species left in existence (most of which are kept in captivity around other parts of the world).
The boat the characters take up the Amazon River is called "Céu Azul", a translation of Blue Sky, name of the production company.
The anteater Charlie was modeled and named after Charles Chaplin, notably for his mute mannerisms and signature bowler hat.
Although Eva is portrayed to be a terrible off-key singer, Bebel Gilberto, who voices the character, is actually a very good singer and accomplished musician.