Type I or giant ELMs, along with sawteeth and disruptions, belong to a class of fast crash or collapse events which occur in JET plasmas. When studied using fast data acquisition, these events are seen to display many features in common. Most noteworthy is their abrupt onset, which can be as fast as 10 microns per s, and their apparent unpredictability. These features are discussed below together with an experiment on ELM control using pellets.