Director Carlos Saldanha became interested in casting singer Bruno Mars in his first voiceover role after seeing him on Saturday Night Live (1975). After working with Mars, he rewrote his character to make him less 'macho' and, after a recording session, had a segment reanimated to fit his singing.
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).
In Rio (2011), after Blu and Jewel escape from the smugglers, Blu can be heard saying "Have you ever heard 'It's a jungle out here'?" In Rio 2, one of the movie's themes is called "It's a Jungle out Here."
In an earlier written storyboard concept, Fernando, the helpful street urchin from the first Rio (2011), was shown to have been adopted as the son son of Linda and Tulio, and would accompany them on their jungle journey, in the process showing his newly specialized skills in field work. Due to pacing reasons, his role was cut down to a cameo at the beginning, where he looks a little bit older than in the first movie.
The trivia item below may give away important plot points.
Nigel is first seen reciting passages from William Shakespeare's Hamlet. His "death" at the end involves an attempt to kill a dueling participant via poison, which is administered to the wrong person, as also happens at the end of Hamlet.