How do you get Sonic goat in goat simulator?

So, I'm curious here, how exactly does one acquire a Sonic Goat in Goat Simulator? I've been playing around with the game and have yet to stumble upon this elusive creature. Is there a specific mission or task that needs to be completed? Or is it a random occurrence that can only be unlocked through certain means? I'm genuinely interested in knowing the process, so if you could provide a step-by-step guide or any hints that might lead me in the right direction, I'd be extremely grateful. Thanks in advance!