Chunky the "Macawnivore" started out as a bit of a joke in the art department. Artist Leighton Hickman was bored with the drab colors intended for creatures in the desert scenes, and painted the saber-tooth tiger with bright "parrot" colors. The filmmakers liked the look for the "Macawnivore" so much that it made it to the final film.
There is much resemblance to Plato's fable of The Cave, a metaphor of the mental limitations people are burdened by. Only a few people can learn to think outside the parameters of convention and "see" the vast, diverse world of possibilities outside of their "cave."
DreamWorks Animation designed Grug specifically with Nicolas Cage in mind for the role. Cage famously turned down voicing the title character of DreamWorks Animation's Shrek (2001) because he didn't like the character's design.
Before this film's release, DreamWorks Animation was suffering from major disaster box office returns and generally mixed word of mouth reception for Rise of the Guardians (2012). While Guardians did gross more than its $145 million budget, it still did not turn a profit for DreamWorks due to its high production and marketing costs, forcing the studio to take an $83 million write-down. This marked the first time the studio had lost money on an animated film since Sinbad: Legend of the Seven Seas (2003). As a result of this combined with other factors, in February 2013, the studio announced it was laying off 350 employees as part of a company-wide restructuring. If The Croods had bombed even worse than "Guardians", the studio would lay off even more employees and face the potential possibility of a bankruptcy. The Croods then opened on March 22, 2013 to glowing positive reviews and widely enthusiastic acclaim from audiences, eventually earning more than $186 million in the U.S. and over $583 million worldwide, earning its place to be sixth highest grossing film of the year (so far), besting Oz the Great and Powerful (2013), Pacific Rim (2013), Star Trek Into Darkness (2013), and World War Z (2013). It remarkably helped DreamWorks' earnings rise higher from $162.8 million to $213.4 million in the second quarter of 2013--one of the best financial earnings ever received in the company's history.
Over the years, the story transitioned from a buddy comedy featuring the characters of Grug and Guy to a family-themed tale with a host of major characters.