He is the grandson of Dracula and Martha (his maternal grandparents) as well as Mike and Linda (his paternal grandparents). Through Mavis, Dennis is also the great-grandson of Vlad (his mother's paternal grandfather). He is also the love interest of Winnie in Hotel Transylvania 2.
Hotel Transylvania 2
Dennis was born 2 years after the events of the first film (June 13th, 2014) to Johnny and Mavis and lived with them at his maternal grandfather's hotel. As he showed a lack of vampire traits, he was raised mostly human, being fed healthy foods and taught by his parents. He often played with the Werewolf kids, and watched Kakie The Cake Monster.
Due to his heritage and possibly his young age, Dennis shows no signs of becoming a monster much to the distress of Dracula. Dennis' lack of powers seem to be because he looks more human like his father than what he is vampire like his mother.
After Mavis and Johnny head to California to visit Dennis' paternal grandparents, Mike and Linda, Dennis is left in the care of Drac and his friends Wayne, Murray, Griffin and Frank. Though, unknown to Mavis, Drac wanting to bring out Dennis' monster genes decides to recruit his friends into putting the little boy through a monster training boot camp.
First, Drac had Frank show Dennis how to scare people by jumping out and scaring two joggers. However, the joggers recognize Frank and ask to take a selfie with him instead. Dennis tries to jump out and scare them. but they just think he's adorable. Next, Drac has Wayne show Dennis how to eat an entire deer, but Wayne being the old wolf that he is forgets how to attack the deer and instead chases a frisbee a nearby human threw for his dog. Finally, Drac asks Murray to conjure up a huge sandstorm to show Dennis how to be a ruthless monster. However, as Murray is performing his spell he throws out his back and only summons a small amount of sand in which Dennis begins to play in and makes a snowman out of.
When all else failed Drac decided to take Dennis to his childhood camp, Camp Winnepacaca where he learned how to use his vampire skills as a kid. However, the trip did not help Dennis as the camp was under new management, and was "too safe".Drac throws Dennis off a tower to teach him how to fly but Drac has to save Dennis from falling to his death. The tower collapses under the combined weight of Griffin, Wayne, Murray and Frankenstein's monster, setting fire to the camp. Mavis was extremely angry when she heard what Drac had done and felt that Drac had betrayed her trust(she had placed Dennis under Drac's care while she went to visit Johnny's hometown),prompting her to seriously consider moving.
When Vlad comes to the party after being invited by Mavis, Johnny has to don a vampire costume. Vlad exclaimed that Johnny's wig looked like "his great-grandma's boobies" but seemed to believe the facade. Upon learning that Dennis was a late-fanger, he volunteered to help Dennis to grow out his fangs. He explained that what he needed to do was take something that Dennis found sweet and innocent (Kakie) and twist it into something terrible. Vlad possessed Kakie the cake monster mascot during his performance to see if Dennis' fangs would pop out, but was interrupted by Dracula as he saw what a traumatizing effect it had on Dennis.
Dennis becomes upset over the arguments between the adults and runs into the woods. Winnie follows him and leads him to her hideout. Bela, who had discovered that Dennis has human blood, tried to kill Dennis, but Winnie got in the way. Bela hits her and Winnie whimpers on the ground. Dennis was enraged and his fangs finally popped out. He quickly turns into a bat and fights Bela, followed by super strength and super speed and enhanced vision allowing him to be able to see that Bela's gang was coming. After Dennis and the rest of the group defeat Bela and his army Dennis asks Drac if he's cool now. Drac reassures Dennis that he was always cool, and that he is perfect no matter what.
Dennis is seen as a sweet little boy with a love of adventure. He seems to have inherited some of his father's personality. Dennis loves his family very much, and seems to understand what's going on around him more than the grown-ups think, such as leaving because he felt he was to blame for Vlad and Dracula falling out and knew the real reason why they were moving without them telling him. When sufficiently provoked, such as his best friend (possible future girlfriend), Winnie, coming to harm, Dennis can go into a blazing rage against an enemy with unstoppable fury. He's also quite smart for his age as he was able to buckle himself into the child seat and slice open his own avocado without any adult help, though he still acts like a child.
Dennis is a little boy with striking red hair and blue eyes, a combination of genes he inherited from both his parents. He is dressed in a sports jersey with the number "4" on it and shorts similar to Johnny. According to creators Dennis inherited Mavis's striking eyes and Johnny's bright hair.
Family and Friends
Mavis is Dennis' mother. She's shown to be very protective of her son, such as making her dad babyproof the entire hotel and even going so far as to consider moving out of the hotel to a place that would probably be safer for Dennis to live (unaware that Johnny, like Dracula, is against it. She is also unaware that Dennis doesn't want to leave either). Due to Dennis' human heritage and lack of any monster abilities, she only feeds him healthy human food, mostly avocados, and has him sleep most of the night. She first appears in the second trailer teased for the second film putting Dennis to bed when Dracula pops up, saying that the lullaby she is singing is incorrect.
Jonathan is Dennis' father. Johnny cares for his son like any other father would, but still maintains his slacker attitude. In contrast to Mavis, who inherited Dracula's over-protectiveness, Johnny's concern is on a normal level; such an example is that she freaked out over Dennis losing a baby tooth.
Due to how much he loves living at the hotel (which doesn't require him to have an actual job to provide for his family), Johnny is willing to cooperate with Dracula to train Dennis as a monster. Unbeknownst to both is that Dennis loves living at the hotel just as much, and hates the idea of leaving.
Dracula is Dennis' maternal grandfather. Since Dennis was born, Drac vowed to always protect him. Dennis likes his "Papa Drac", who often amuses him by causing self-harm. Dracula has been waiting for the day Dennis gets his fangs, but becomes concerned as his 5th birthday nears, which is when the chance completely vanishes. Dennis is taken to various spooky places by his grandfather, to inspire his inner monster to surface. In the movie, Drac is all for Mavis and Johnny to go visit Johnny's parents in California so when they leave, Drac and his friends put Dennis through "monster training boot camp"
Vlad is Dennis's maternal great-grandfather. When Vlad finds out that he has a great-grandson, he goes to the hotel and when he sees Dennis still doesn't have his fangs, he thinks he is a "late fang-er" like his son Dracula. So Vlad tries to "scare" Dennis's fangs out by possessing Dennis's favorite monster Kakie the cake monster. Vlad at first rejects accepting Dennis for who he is, (half-human), but after seeing Dennis defend his family and friends from Bela, he learns that it doesn't matter that he's part human and accepts Dennis as a part of the family.
Frank, Wayne, Murray, and Griffin
In the second film, is is shown that Dennis has a nephew/surrogate uncle relationship with his Grandfather's friends. In the first teaser trailer for Hotel Transylvania 2, the four were genuinely concerned when Dennis didn't fly after Dracula tossed him over the tall tower during part of his monster training, and until Dracula actually saved Dennis from hitting the ground, they kept pointing out how Dennis wasn't flying and kept urging Dracula to get him, and Murray got freaked out when Dennis started getting too close to the ground.
Wayne and Wanda's well-behaved daughter. She is Dennis' friend, though she is shown to have a crush on him and considers him her zing. Her normal greeting is pouncing on Dennis and licking him. She considers him the kindest boy she knows due to her unruly brothers usually causing havoc and chaos. While he says that he and her are just friends, he care about her greatly and seeing her hurt by Bela causes him to go into a rage and unlock his vampire powers.
Despite their feelings for each other, Winnie and Dennis have not actually zinged with each other yet. In Hotel Transylvania 3: Summer Vacation, Dennis is shown to feel slightly uncomfortable when Winnie kisses him, and later, he tries to avoid eye contact when she flirts with him in order to make them zing with each other. According to Dennis, he is too young to zing; this could be attributed to him not being emotionally mature enough yet to face having such feelings for his best friend.
Mike and Linda
Mike and Linda are Dennis's paternal grandparents. They love Dennis, but like their daughter-in-law, Mavis, wonder if it Hotel Transylvania is a safe place for him to live, mostly due to his lack of monster abilities.
- Due to his heritage as the son of a vampire and a human, Dennis is a Dhampir, a half-vampire/half-human hybrid however the term was not used in the second film.
- Dennis' favorite superhero is Batman.
- With the exception of having blue eyes like his mom, Dennis looks just like his dad.
- As a baby, Dennis was taught the words "Bleh, Bleh-Bleh" by his mother to annoy Dracula, and they were his first words.
- Taking into consideration humans are not immortal, and while it's unknown if Dennis himself is immortal, he will most likely live a very long life, likely long outliving his current paternal relatives.
- Dennis' nickname by Dracula, Denisovich, is considered Russian by fans.
- Dennis' hair was originally going to be a lot larger. However, the animators had trouble with animating all the hair, and found it to look awkward when Dennis was being hugged or held by people.