Spoiler: Valamir
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You know enough about magic to deduce the Baron is likely using Mage Hand to levitate the unicorn plushie (Prestidigitation would also work, because the toy isn't heavier than 1 pound) and Ventriloquism to make it talk. He's either casting his spells Silently, or else has blended his verbal components seamlessly into his comedy act. A mix of Ghost Sounds and Prestidigitation explains the various audio effects. There are other possibilities, but this is the parsimonious one.

((Remember, we're using invisible and automatic perception and knowledge checks. If there is anything dangerous or curious about a scene, or if you have pertinent knowledge, you'll get that information if and when you pass your checks. DO prompt me for additional information if, like here, you want to know something specific that I may have overlooked or just glossed over -- like knowing exactly how the act is done.))


"Boo!"
"Get a real job!"
"You suck!"

The three Varisian men in orange wandered over during the performance, apparently, solely to heckle the Baron.

Undeterred, the Baron continues to plead for his soul while Fluffy turns menacingly towards the thugs. "Hey, I don't come down to where you work and slap the **** out of your mouth!"

Aside, "Language, Fluffy, this is a family show!"

"This doesn't concern you, Stan! Why don't you juggle or something while I deal with these pricks?"

While the three men fume, they're too taken aback by the verbal assault from a puppet to say or do anything.