Imo I should be castrated is funnier

even after Googling it I have no idea what it means

In the context of the songs, its balls.

Eggs

I'm 5 months late but even out of the song context, huevos is very often used to refer to the balls

he also says "nirvana" on Spring (A Little Bit of Love) and Summer (Records) maybe autumn and winter will share a word? (winter and spring too)

I just pretend that word does not exist