Based on your search for "Los Simpson capítulos completos en castellano," here is the current situation regarding where to watch the series: 2013 Rom Iso Install: Inazuma Eleven Go Strikers
Currently, there is no legal streaming platform that offers all seasons of The Simpsons in Castilian Spanish (Spanish from Spain) in one single place. The rights are split between different platforms. P3danalyzer156beta New
Here is where you can find them: