Urgh. More stupid grammar things annoying me tonight.
Someone used the phrase "it was like a lightbulb went off in my head". What, so you had no idea about whatever the thing was? Because that's what you just told me.

Lightbulbs light up when you have an idea or realise something. It means you can see.

A flashbulb goes off - well, flashes - again providing brief illumination of a subject. It's different to a lightbulb in this context though.

I bet this person says "nip it in the butt."