Some workers in a washing machine factory

 Some workers in a washing machine factory decide that they want one for themselves. So, they resolve to steal the parts over time and build it in their apartments.

But it seemed that every time they tried, it would end up as a T-34.

Variants tend to change up the goods produced, both alleged (samovars, cradles) and actual (AK rifles, machine guns). Some ascribe different motives to the workers, or have them confessing to the theft. But the central theme that they never realize they're building military equipment remains.