SunriseShine88 brought up a point about me using the number 17 in my fanfic "Ol' Fools Day". So I wanted to explain the significance behind it here as well.

So, as you Undertale fans know, there is a special entry in the true lab... Entry 17.

DARK DARKER YET DARKER

THE DARKNESS KEEPS GROWING

THE SHADOWS CUTTING DEEPER

PHOTON READINGS NEGATIVE

THIS NEXT EXPERIMENT SEEMS

VERY

VERY

INTERESTING

...

WHAT DO YOU TWO THINK?

This entry most likely correlates with Sans, another monster, and the Royal Scientist.

So, I use that number in my fanfics that have to do with Sans, because in my perspective, that number does hold a huge significance to his character.

It doesn't have much to do with the story-line in the fanfic, other than it being a little Easter Egg.