In recent years, Python has become the language of choice for data scientists with its many high-quality scientific libraries and Scala has become the go-to language for big data systems. In this paper, we bridge these languages with ScalaPy, a system for interoperability between Scala and Python. With ScalaPy, developers can use Python libraries in Scala by treating Python values as Scala objects and exposing Scala values to Python. ScalaPy supports both Scala on the JVM and Scala Native, enabling its usage from data experiments in interactive notebook environments to performance-critical production systems. In this paper, we explore the challenges involved with mixing the semantics and implementations of these two disparate languages.