Alexei is a major character in Season 3 of Stranger Things.
He is a Russian scientist who was forced into working on the Key beneath the Starcourt Mall. Alexei has no fluency in English and can only speak Russian.
After Alexei’s co-worker failed to get the Key to work he was executed by Grigori, Alexei and a fellow scientist were then given one year to have the Key work properly.
1985
Alexei stopped having to work on the Key after he was arrested by Jim Hopper. Alexei then went on the run with him, Joyce Byers, and later Murray Bauman.
Alexei communicates with the other characters with the help of Murray, who is fluent in Russian. Alexei later explained the reason for the secret Soviet presence in Hawkins was because of a device known as the “Key” that he and his colleagues were trying to construct, which they had failed to do Russia on numerous occasions. The “Key” was able to unlock a “doorway between worlds”, Alexei’s way of articulating the concept of a Portal to Murray. Upon this being translated, Hopper, Joyce, and Murray then proceeded to return to Hawkins with Alexei with the intent to close the Russians’ Gate.
Later Alexei, Murray, Jim and Joyce went to the Fun Fair to search for the kids, Alexei thought he couldn’t go in the Fun Fair because he wasn’t American. Murray said he didn’t have to be American to go in, and they both entered the Fun Fair. Alexei later won one of the carnival games, and he got a Giant, Stuffed Woody Woodpecker. He was later killed by Grigori, a Russian hitman, after he attempted to defect to the United States and was briefly left unattended by Bauman.
Personality
Alexei had a very childlike personality. During his brief partnership with Hopper, Joyce and Murray, he was shown to enjoy Slurpees and cartoons (such as Woody Woodpecker and Looney Tunes) and longed to join in the festivities at the Hawkins 4th of July Fun Fair. Alexei was also overjoyed to win a giant stuffed Woody Woodpecker at the fair moments before his death.
Whilst Alexei was mostly friendly to his captors, at times he was shown to have a cunning side, only offering his knowledge of the Russian's operations in exchange for things that benefit him, such as his favourite cherry-flavored Slurpees. When he received a different flavor, Alexei refused to help until he got what he wanted.
Despite this, the second Alexei is threatened or physically assaulted by Hopper his cocky side instantly drops and it is revealed Alexei is very fearful of authority figures punishing him. This is shown again when he decides against trying to escape back to his comrades, as he is smart enough to recognize that if he returns alive (but still harmed), they'll know he has been giving secrets away and likely torture and kill him.
Alexei was easily entertained, amazed at the sight of the 7-Eleven and the numerous items for sale, as well as the 4th of July Fun Fair and winning a prize, likely due to these absent luxuries in the USSR. He also shows great accuracy and precision, as he won a game of Balloon Darts without missing a single balloon.
Alexei enjoyed the American way of life and was willing to defect from the USSR and even asked Murray about becoming a US citizen after helping them stop the Russians.
Gallery
The next day, Alexei sees Hopper hand him the food that he requested.
Alexei tucking his napkin into his shirt.
Alexei eating his burger.
Alexei drinking his Slurpee as Murray begins to question him.
After drinking his Slurpee, Alexei is disgusted after realizing it is strawberry-flavored.
Alexei wiping himself with his napkins.
(in Russian) "Tell that stupid man it is not the same in the slightest, and I would like the cherry I requested."
Alexei chuckling as he watches Woody Woodpecker on TV.
(in Russian) "No cherry. No deal."
Alexei giving Hopper a cocky smirk.
Alexei being threatened by Hopper.
Alexei having been thrown outside by Hopper.
Alexei managing to uncuff himself.
Alexei grabbing the car keys that Hopper had discarded.
Alexei having gotten into the car.
Alexei starting the car to make his getaway.
However, Alexei stops driving when he realizes his superiors will likely kill him if he revealed any information.
Alexei returning to his captors and admits to Hopper he likes strawberry Slurpees too.