During Russia’s surreptitious invasion of Crimea, much was made of the “little green men,” soldiers without insignia who turned out to be Russian regulars.

On Monday there was a new green man — albeit one of a decidedly different political hue — the opposition leader Alexei Navalny, who was doused with a bright green liquid in the Siberian city of Barnaul by an unknown assailant who had pretended to shake his hand.

Mr. Navalny wrote on his Facebook page that he initially feared an acid attack after feeling a burning sensation. But relief appears to have given way to exaltation after he realized that the bright green liquid not only would not harm him, but even made him look like a superhero — in his eyes, anyway. He can be seen mugging for the camera in a selfie taken after the fact.

Referring to masked heroes in Hollywood films in a post on Twitter, he wrote: “I will be opening a headquarters in Barnaul as if I am from the film The Mask! Cool. Even my teeth are green!”