If you want to do it with the randomness, I can think of a couple of ways:
1: Create a "Piercing Howl" event that does nothing but call a common event.
Have that common event display the text, and then Force Action (Immediate) the Confusion skill.
(That's necessary because normally a Common Event called with a skill activates after the skill runs, which isn't what you want.)
2: You could always import the text "The Den Mother lets out a piercing howl" into the animation frames of the spell, and customize the animation for the version that the Den Mother uses. (Okay, this wouldn't work like Show Text, but I wanted to bring up the point that you can do a lot with creating custom animations.)
...
...
...am I a bad person for imagining the Den Mother letting out a piercing howl as a middle-aged housewife leading a pack of killer Cub Scouts?