Vovochka is the Russian equivalent of Little Johnny. He interacts with his school teacher, Maria Ivanovna (shortened to Marivanna; a stereotypical teacher's name). "Vovochka" is a diminutive form of Vladimir, creating the "little boy" effect. His fellow students bear similarly diminutive names. This "little boy" name is used in contrast with Vovochka's wisecracking, adult, often obscene statements.
In biology class, the teacher draws a cucumber on the blackboard: "Children, could someone tell me what is this?"
Vovochka raises his hand: "It's a dick, Marivanna!" The teacher bursts into tears and runs out.
In a minute the principal rushes in: "All right, what did you do now? Which one of you brought Maria Ivanovna to tears? And who the hell drew that dick on the blackboard?"