As the title says, putting a generator on FloatLizards (both regular and xmas) causes them to always spawn a copter when shot down, regardless of what setting you may choose beforehand.
This seems to be a symptom of the generator event's parameters essentially overwriting whatever settings you made to a given event prior to adding the generator. It's something that seems to affect essentially all events (for example the shootable spike balls completely break once you apply a generator to them).

For most events it's a non-issue as they either have no parameters or they don't exactly despawn to begin with, but flying lizards are a regular enemy someone might actually want to respawn and do so without worrying about copters undermining level design.