Dialect syntax has proven to be an invaluable data source for theoretical syntax, and theoretical syntax has provided useful analytical tools for uncovering fascinating grammatical properties of dialects. In the 1980s, the assumption that there must be more than one structural position in the left periphery of the clause was confirmed (among others) by so-called -doubly filled COMPs- in Bavarian (e.g. the co-occurrence of a wh-phrase and a complementizer), and in the 1990s, Northern Italian dialects provided the main empirical evidence for Rizzi's extended theory of the left clausal periphery...