When Betelgeuse did it, it scared the heeby jeebies out of me.
I though it was going to blow up right there and then right in front of my face.
I went so far as to phoning my astro buddy that night. As that star is so big and orange anyway, sitting low in the atmosphere, it got very big & very colourful and scary. This was before I understood about how the low horizon and atmospheric turbulence can affect stars. I felt a bit silly afterwards.
But if I hadn't asked someone, I wouldn't have known myself.
