  This is a colloquium talk in CAU, Kiel delivered on June 7, 2024 on the
occasion of Walter Bergweiler's retirement. Walter's work on meromorphic
functions consists of two parts: generalizations of Picard's theorem to
differential polynomials, and the applications of the rescaling principle known
as the Bloch Principle. Since the talk was aimed at the general audience, a
brief introduction to Nevanlinna theory is included.
