When Weasels become agitated, they immediately begin to do this. The general action is for the weasel to shake uncontrollably, turning back and forth, with eyes wide and mouth open, tongue sticking out. Weasels may use this as an attack or just to scare away people. Ogling, however, has an effect on their crazy blood-driven rage and calms them down.
Derivatives of Flipping the Fuck out are used exclusively by the Weasel King, one being "Pondering the Fuck out" when he is concerned about the ultimate fate of the universe. The most powerful flipping out, however, is the Weasel King's "Final Flip Out", wherein the aforementioned king fuses with Problem Sleuth (who is also using Sepulchritude) and the two combined deal massive damage, capable of eliminating the hundreds of health meters of Demonhead Mobster Kingpin in short order.
It isn't said directly that Doc Scratch flips the fuck out, but what he does is
Sollux asks Aradia to calm her robot versions down because they're
In [S] Collide, Hussie flips the fuck out like a weasel while in Homosuck mode.