Nikolai better known as Thomas is a recurring character from Regular Show. He intitially appeared as an intern for the Park at the beginning of the fourth season in the episode "Exit 9B". It was later revealed that he was a Russian spy by the episode "The Real Thomas" in Season 6.
When Nikolai first appeared in the episode, "Exit 9B", he was shown to be a loyal individual who is willing to serve those at the park as an intern. Throughout most of his appearances, Nikolai kept up his façade as the average young adult who works at as an intern for benefits in the future. Nikolai was also very charismatic and affable to his friends like Mordecai and Rigby. At times, Nikolai detest the cruel pranks done by Muscle Man but got used to it. When he was about to get fired by Benson for being a burden to the park, Nikolai was willing to help the park men against his rivals to gain their trust.
In the Episode "The Real Thomas", Nikolai revealed his true identity as a ruthless Russian spy who never truly cared for the Park but care to take it to help his home country Russia. After witnessing Natalie's cold personality and remembering the good times with the men at the park, Nikolai decided to terminate the mission and save his friends. Seeing himself as a irredeemable traitor to his friends and his home country, Russia, Nikolai decides to live a new life from those he had wronged.
Nikolai is an exceptional martial artist who knows many techniques that can knock out his opponents. Nikolai can easily knock out his opponents with many types of holds and has fast reflexes. As a spy, Nikolai is one of the best in his home country, Russia. He was great enough of a fighter and a genius that he was tasked with the dangerous mission of securing the park for Russia. Compared to Natalie, Nikolai is a formidable martial artist.
As a fighter, Nikolai has not shown any weaknesses.