Sparks are flying
When a person has such nerve that their imaginary testicles are so large they are actually dragging on the ground producing sparks.sparks flying
When two people hit it of romantically
Sparks fly
A vague phrase that apparently has lovey-dovey connotations. Flying sparks makes for a great screensaver or background to a music video w/ lyrics, but how it's supposed to allegorize love... I do not know. Recommended to say in a uwu voice.