Probing Day is an Irken occasion on which The Tallest contact all of the Irken Invaders on duty, and check up on how far each has gotten in their missions to conquer their assigned planets. This generally involves the Invaders having to give a presentation of sorts like an essay or video presentation, depicting their current plan to subjugate or kill their planets' inhabitants. However, the current Tallests have added some ideas of their own to the procedures: As of the most recent Probing Day, each Invader has to deliver a puppet show; failure or refusal to do so will result in the contactee getting pummeled by a pair of mallet-wielding robotic arms, remotely controlled by the Tallest. This is called a "pummeling." Probing Day was witnessed in the episode "Walk for Your Lives".
Probing Day is the only known holiday celebrated by the Irken race.