So, you accidentally stick a regular clear bulb in your Christmas lights (fairy lights [US] ?) instead of a fuse bulb. Next time there's a bit of a surge, there's no discernable weak point in your circuit and it takes out more than one bulb. Where do you start debugging that?
Sure, you could sit with a multimeter and probe all the bulbs to find the duff ones. Have you ever tried to attach multimeter probes to a fairy light bulb?!?! It's a nightmare. Specially when you only have 8 fingers and two thumbs.