At the moment I wrote that I considered it funny. But to be honest, I was very tired and I'm afraid my mind got a little bit twisted. So I mistook ovaries for egg cells (ova), which are the really microscopic things. The idea was that she would cook them and to check their shape a microscope would be neccessary and this might fa ll into the pot and whatever … – it's weired, just forget it.

Having said that, I'd like to try some clarification.
Although testicles are called balls they have the shape of eggs (which might explain that german slang word). Ovaries (not ova) also have the shape of eggs. Therefore your conclusion that ovaries look more or less same as balls is totally understandable.
I just wonder if the word "balls" for testicles was inspired by the rugby ball or the football or something completely different.