After her boss fell sick, she willy-nilly found herself directing the project.
Willy-nilly zoning laws.
So people chasing money churn out novels willy-nilly.
The novel Alice in Wonderland describes a place where random things happen all willy-nilly.
Origin of willy-nilly
- Alteration of will ye (or he or I), nill ye (or he or I) be you (or he or I) willing, be you (or he or I) unwilling
From American Heritage Dictionary of the English Language, 5th Edition