Dennis "Denisovich" Dracula-Loughran is the half-human/half-vampire son of Jonathan and Mavis. He is also 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 maternal great-grandfather; his mother's paternal grandfather).
Dennis is a little boy with unruly, 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.
Dennis is outwardly portrayed as being optimistic and childish such as any child is age. He appears to have a fairly similar temperament to Johnathan: easygoing, insouciant, and exuberant in most scenarios. Aside from his high-spirited demeanor, Dennis has substantiated noticeable signs of maturity for his age - even as a five-year-old he finds himself too old for any childish needs Mavis attempts to provide him with. Overall, he is rather naive about certain things; he expressed a large amount of naivety when he lacked any sort of monstrous abilities. Initially, Dennis is unaware that his lack of vampire skills was an immense problem and would impact him negatively; when he is exposed to the realities of the world, Dennis began taking this fact more seriously, attempting to become a vampire in order to remain at Hotel Transylvania.
Hotel Transylvania 2
Dennis was born 2 years after the events of the first film (June 13th, 2013) to Johnny and Mavis and lived with them at his maternal grandfather's hotel. Accordong to Mike (his paternal grandfather) Dennis was named after Mike's father (a great grandfather). According to the height chart, "DENNiS 1 YEAR!" was taller than "Mavis year 1", but "DENNiS 2 YEARS!" was not as tall as "Mavis year 2".
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 he loved to watch Kakie The Cake Monster's show.
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 his vampire mother.
Monster Training Boot Camp
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, 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 the camp on fire. Mavis was extremely mad and upset 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.
Then Dennis and his family go back to the hotel to continue finishing his 5th birthday party. Dennis is seen dancing with his father Johnny, his mother Mavis, and Winnie. Dennis then freezes Linda in place. Dennis is last seen dancing some more with Winnie. Just then, Dennis sees his birthday cake and flies up to blow the candle out on his birthday cake, however, just as he about to blow out the candle on his cake, the Elderly Gremlin eats his entire cake which stuns Dennis as the Elderly Gremlin says she didn't do it.
Hotel Transylvania 3: Summer Vacation
- According to creators Dennis inherited Mavis's striking eyes and Johnny's bright hair.
- 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.
- It is unknown whether he will get his father's mortality or his mother's immortality, but he might live slightly longer than true average purebred humans, but having vulnerability to death, as a combination of the two.
- Dennis (being half human) does not burn in daylight, but he dislikes the sunlight and prefers nighttime. This is likely due to his vampire heritage.