"New is always bad, never not be afraid."
- Grug's former motto
Grug Crood is the main protagonist of The Croods.
As the father figure of the Crood family, Grug is initially overprotective, worrisome and extremely patriarchal. He teaches his children his own motto of "never not be afraid" and reinforces these teachings with constant story-telling regarding Krispy Bear which all end in "he saw something new and died". His youngest son, Thunk takes his fathers lessons to heart but is very gullible and indecisive opposed to Eep who never listens to Grug and is much more self-reliant. This proves that although Grug does possess pure intentions his attitude towards his children can be self-destructive and short-sighted. He also appears to have the most attachment to the cave, he was visibly saddened over its destruction and describing it as "cozy".
Grug also has a violent temper, can be more brawn than brains and appeared to be anti-intellectual. He detests the use of having a brain and thought that caveman didn't need to have an IQ as long as they had their brawn. He can be rather impulsive and not thoroughly educated, for example after Thunk was caught on fire Grug suggests to "hide from it in the tall, dry grass". Despite his anti-intellectual nature he can develop very intricate and clever ideas such as the rug, shades, mobile home, snap-shot, self-tightening belt, ride and lifterator. The greatest display of Grug's intelligence was when he used the Pirahhnakeets to escape his death.
Grug has a deadpan and at times violent sense of humour. He was visibly elated when he thought Gran had died and later disappointed over discovering she was still alive. This is further shown when after Gran states she would never survive the journey, Grug enthusiastically states "let's do it." He seems to have developed a better grasp of humour, and while about to throw Guy across a chasm, he remarks that he wanted to "throw you away ever since I met you" and when Guy responds "is that a joke?" Grug confusingly responds "what's a joke".
His devotion to his family made him a very loyal and selfless person. For example he protected the Croods from the falling rubble, at the risk of injuring himself and saved his family by throwing them across a chasm, knowing he would not be able to join them.
Not much is known about Grug's background, but it is revealed in the beginning of The Croods that his family has aheard and followed a strict set of rules and regulations for generations, and so, his family's cave are full of hand prints from previous inhabitants. At a unknown point before the movie, he met Ugga Crood, his wife. o
Grug is the 39-year old overprotective father of the family who dislikes the outside world. But when his home is destroyed, he embarks to find a new home for his family. He also has to deal with his family and especially his older daughter Eep from falling for Guy, though he ultimately accepts Guy into the family.
- Grug's overprotective behavior had caused him to be an antagonist but, he was not meant to be a villain and not even close to being an anti-hero.
- Grug's inspiration is Marlin who was the protagonist of Disney and Pixar's Finding Nemo and he is also similar to Fred Flintstone.
- Grug likes to tell stories about Krispy Bear.
- Grug is also the name of a series of story books called Grug.
- Grug has been shown to possess quite the skills as an artist, which can be seen near the climax of the movie in which he imprints images of his family in the rocks in a cave.