From the Super Mario Wiki
Harrassimentia Phlyoverus is a class of enemies from in Super Mario World 2: Yoshi's Island. The species from the class appear in later games; this is the only time, however, that they are referred to as members of a class. The name "Harrassimentia Phlyoverus" is a corruption of the word "harassment" combined with an etymographic misspelling of "fly over us".
All members of this class have the ability to fly, often with wings, but in one case, with propeller hats.