Trivia: Vin Diesel was given a special "Groot" version of the script that contained "translations" of what Groot was actually saying whenever he utters his one and only repeated sentence "I am Groot." This was done to help him deliver his dialog appropriately, since he would know exactly what point Groot was trying to get across with each line. Reportedly, only Diesel was given this version of the script - in everyone else's script, Groot's dialog is merely "I am Groot" over and over again.
Trivia: James Gunn's parents, James Sr. And Leota, make cameos in the film as "Weird Old Man" and "Weird Old Man's Mistress."
Trivia: Spoiler. Writer/Director James Gunn spent months trying to figure out a way to end the film without killing off the character Yondu, as Yondu's actor Michael Rooker was a close friend of his and he wanted the character to be in the planned third film. But he ultimately decided that Yondu's redemption and self-sacrifice to save his surrogate "son" Peter was far too important to the theme of fatherhood in the film, and went ahead with killing off the character. Rooker was a bit crestfallen at first when he found out about his character's death, but ultimately agreed with Gunn's decision.
Trivia: During one of the mid-credits scenes, we see Sylvester Stallone assembling a team of old ravager buddies. The member that is a disembodied head ("Mainframe") is actually voiced by talented-but-controversial singer Miley Cyrus in an uncredited cameo. Director James Gunn thought her unique sense of spunk and energy lent itself well to the character.
Trivia: The wide-shots that show the entirety of Ego the living planet are actually some of the most complex visual effects shots ever, at least in terms of size and scope. One VFX artist has stated that the digital model is about equal to a polygon count of close to one trillion, as they added as much detail as was possible.
Trivia: SPOILER: Stan Lee's cameo shows him discussing his time as a FedEx employee (a nod to his cameo from "Captain America: Civil War") and presumably his exploits from other MCU films to a group of large bald humanoid beings. These beings are known as Watchers, who are an alien race whose sole purpose is to observe events throughout the universe. This is in keeping with a fan theory that Stan Lee's cameos within the MCU (and possibly Marvel films that are not part of the MCU) point to him being a Watcher himself, or at least someone that reports to them as this film would suggest.
Trivia: The 80's Sony Walkman and headphones seen in the film were built from scratch, as the ones used in the original film were somehow lost and the production had a great deal of trouble finding real ones that worked for a reasonable price. As they hadn't been produced in close to 30 years, it ended up being cheaper and easier for the prop team to just build close approximations.
Trivia: SPOILER: During the third mid-credits scene, we see the high priestess Ayesha reveal that she is creating a being to destroy the Guardians, and that she will call him Adam. This is Adam Warlock, who in the comics is a being that was genetically engineered to be perfect and is Ayesha's "brother." He also played a very important role in the "Infinity Gauntlet" and "Infinity War" comic book storylines that the next "Avengers" films were based on, although the character didn't appear in the movies.
Trivia: When Nebula and Gamora come across the skulls, one of the skulls has a horse-like shape to it. This is a reference to the character Beta Ray Bill, who in the comics was one of few characters worthy enough to lift Thor's hammer. Or possibly Kymellians - horse headed aliens closely associated with the preteen Marvel team, Power Pack.
Trivia: Jeff Goldblum makes an appearance as the Grandmaster during the credits. You can see him dancing in the sidecards along with the other Guardians after the mid-credits scene with the Sovereign High Priestess. This marked Goldblum's first appearance as the character, six full months before he was featured in "Thor: Ragnarok."