We consider a model in which gamma-rays in blazars are produced during encounters of relativistic blobs of plasma with radiation field produced by luminous stars within the jet. The blob, formed in the inner part of the jet, already contains relativistic electrons which comptonize stellar radiation to GeV-TeV gamma-ray energies. These gamma-rays can initiate the Inverse Compton electron-positron pair cascade in the radiation field of the star within the jet. Such a scenario might be responsible for the appearance of short time scale gamma-ray flares. The star collision model can explain the appearance of the extreme orphan gamma-ray flare observed in the GeV and sub-TeV energy range from the flat spectrum radio quasar PKS 1222+21.