It is a real and rare medical condition.
Cause - Its a dermoid cyst having benign congenital growth. It occurs on eye surface when cells meant to function as hair follicles , sebaceous gland and other tissues get trapped in it during embryonic development. Its surprising but yes actual hair growing on eyeball.
Effect - hair strands growing on eyeball, whitish yellow visible mass on eye , irritation and visual issues if it affects vision
Treatment -
If its harmless and not causing problems then it can be left without intervention
If it causes discomfort and visual issues then it can be removed by surgical excision