There is a theory behind the gender change of Data's cat "Spot".
Early in the series, Spot was referred to as a "he", however Spot later gave birth to kittens in the de-evolution episode. (Genesis - Ep. #71)
The theory claims he was the unfortunate victim of a transporter malfunction, turning him into a "she."
In this event, the transporter (quite literally) ate Spot's balls.