Bulb and Fill Up

Bulb

A bulb is a shaped piece of glass that holds a thin piece of filament which heats up to provide light. A bulb may come in several shapes, but is usually rounded.
Ex: We are going to need a replacement bulb for the hallway light fitting. It blew when I turned the lights on this morning.
Ex: A flight student's first time in the cockpit of a passenger jet can be an overwhelming experience. Just looking at all the switches and bulbs on the control panel allows one to see the complexity of the job of a pilot.

To have a light bulb moment means to have a good idea or solution that pops into your mind quickly. The idea behind this expression is that the idea is a bright one, or sheds light on a problem.
Ex: We were stuck on the side of the road with engine problems when Sergio had a light bulb moment, remembering that his cousin, who is a mechanic, lived just off the next exit. We were able to contact him by phone within minutes.
Ex: I was hoping for a light bulb moment to get me out of the situation that I'd created, but no matter how hard I thought, no ideas came to mind.

Fill Up

A fill up is when you put gasoline or another fuel into your car's tank or get gas. When you fill up at a gas station, it usually means you are completely filling your tank with fuel until it can hold no more, you are filling up to capacity.
Ex: I'll be glad to follow you to the restaurant after the show in my car, but as I am running low on fuel, I'll have to stop for a fill up.
Ex: Richard wished he had stopped to fill up his tank earlier. Now that he saw the long bridge ahead, he was beginning to think his idea of saving time by skipping that step was a risky one.
The expression to fill someone's shoes means to take on the position and/or responsibilities of a person who is no longer present. The idea in the expression is usually used to say that the person who has departed did a good job in the role and therefore left big shoes to fill, or a challenging task in replacing them.
Ex: As we all know, it will be extremely difficult, if not impossible, to fill Michael's shoes after all that he has done for this tennis club.
Ex: As the faculty mourned the loss of one of their dearest friends and colleagues, the college president contemplated the task of replacing the beloved professor, who had left big shoes to fill.