|Alexei Nikolaevich Romanov|
|Singing voice actor(s)||N/A|
Alexei shares the same fair skin, auburn hair, thick eyebrows, and light blue Romanov eyes as his sisters Olga, Tatiana, Maria and Anastasia. A large fringe covers his left eye.
His limited appearances in the film portrayed him as a playful boy who was fond of his fourth older sister Anastasia and wanted her to join in on the fun.
Alexei, the heir to the Russian throne, was one of six members of the Imperial family who died in the revolution by the Bolsheviks as a consequence of the curse cast by the power-mad sorcerer Grigori Rasputin. He later reappears in the film as a ghost in the ballroom of the Catherine Palace during the "Once Upon a December" sequence and as a figure in the nightmare concocted by Rasputin to lead Anastasia to her death in the North Sea, though the scheme fails, thanks to Dimitri.
- According to the film, Anastasia was 8 years old rather than 17 at the time of the revolution. In addition, the film also states that the revolution occurred in 1916 as opposed to 1917. This implies that Alexei, who was three years younger than Anastasia in real life, died at the age of 5 instead of 13.
- In the nightmare concocted by Rasputin, Alexei is the first of the Imperial children to appear to Anastasia, beckoning her to play with him. The two siblings shared a close bond in real life.
- In the nightmare concocted by Rasputin, Alexei wears a sailor suit, a common sight in photographs of the historical Alexei.
- At a height of 5'6" (1.68 m), the historical Alexei was much taller than his animated counterpart.
- Although Alexei suffered from a blood disorder called haemophilia in real life, few references to his illness appear in the film, barring a scene in the "Once Upon a December" sequence in which the Tsarevich and his family approaches Anastasia in the ballroom of the Catherine Palace with a slight limp to his walk. However this could be explained by Anastasia not knowing what Alexei suffered from in her youth as she was too young to have known exactly what was wrong with him, explaining the lack of references to his illness in Anastasia's subconscious and the subtle nod to it in the ballroom.
- It is unknown why unlike the rest of his family that had supposedly "grown" within the ten year separation from Anastasia, Alexei is still portrayed as a ghost child, when he should had been "matured" into a teenager of 15. Considering that he was the "baby of the family" and that he was murdered at the age of 5, it is possible he stayed a child since he was three years younger than his only sister that survived the revolution, or simply the fact that through Anastasia's memories she somewhat preserved him still as her "baby brother" and was far too young to be even be aware of the brutality of the revolution. However in Anastasia's nightmare he did look older than he was portrayed in "Once Upon a December".
- Eerily enough, Alexei's image in the family portrait, which had incorrectly portrayed him with light blonde hair, shades an uncanny resemblance to Prince George of Cambridge, whom is also the heir of his kingdom's throne. Ironically, George's great-grandfather, Prince Phillip, is the Tsarina Alexandra's great-nephew through his mother who was her sister, therefore Alexei and George are related.
- Before the birth of Alexei, Nicholas is said to have contemplated lifting the ban on female rulers in Russia established by emperor Paul around 1800 making older daughters in line before sons born after them. On the family portrait the oldest girl, Olga, is the only person sitting in the painting in attire apparently modelled on the imperial robes of her father. This can be interpreted as that she was heir apparent, not the sickly and weak Alexei.
- If the Tercentenary Ball at the start of the movie happened on the same day as in real live (February 21st) then Alexei would have been 4 and not 5 as his birthday wasn't until August of that year.