The 'fast light' effect has been observed when studying interaction of modulated microwave signals with a cryogenic resonator. The effect manifests itself as a time advance of the peak of the reflected pulse relative to that of the modulation pulse. The effect is much more pronounced for the phase-modulated signals, as compared to the amplitude-modulated ones. We show that 'fast light' is a pulse-shaping phenomenon, which depends on parameters of the modulation signal, and is not related to superluminal pulse propagation. We also discuss possible applications of the 'fast light' to pulse control and generation of complex waveforms at microwave and optical frequencies. ; E Ivanov, J Bourhill, D Creedon, J Hartnett and M Tobar