Given a family of real probability measures (µt) t≥0 increasing in convex order (a peacock) we describe a systematic method to create a martingale exactly fitting the marginals at any time. The key object for our approach is the obstructed shadow of a measure in a peacock, a generalization of the (obstructed) shadow introduced in [13,46]. As input data we take an increasing family of measures (ν α ) α∈[0,1] with ν α (R) = α that are submeasures of µ0, called a parametrization of µ0. Then, for any α we define an evolution (η α t ) t≥0 of the measure ν α = η α 0 across our peacock by setting η α t equal to the obstructed shadow of ν α in (µs) s∈[0,t] . We identify conditions on the parametrization (ν α ) α∈[0,1] such that this construction leads to a unique martingale measure π, the shadow martingale, without any assumptions on the peacock. In the case of the left-curtain parametrization (ν α lc ) α∈[0,1] we identify the shadow martingale as the unique solution to a continuous-time version of the martingale optimal transport problem.Furthermore, our method enriches the knowledge on the Predictable Representation Property (PRP) since any shadow martingale comes with a canonical Choquet representation in extremal Markov martingales.