  Despite significant progress in both data taking and the development of
theory, blazars keep offering surprises. While many frequency bands are now
covered by long-term monitoring efforts on at least a few selected sources,
blazars remain unpredictable and the same source may exhibit vastly different
behaviors. Here, an overview is given about four selected sources, namely 3C
279, PKS 2155-304, PKS 1510-089 and CTA 102. All of them exhibited, indeed,
highly unexpected events.
