Brightly anonymous

I haven't a clue what these flowers are. Neither did my sister, in whose garden they were growing - they apparently just appear. Anyway, on an annoying day of showers at inconvenient moments and a tooth that seems intent on disintegrating before it can be crowned, these were quite the brightest subjects for a photo that I came across. If anyone can tell me what they are, that would be an added bonus - they're cheerful little things.

I'm seeing the dentist in two days ...