Formal:
* The witness's unexpected testimony left the jury nonplussed.
* The professor's complex theory left the students nonplussed.
* The sudden change in plans left the organizers nonplussed.
Informal:
* I was totally nonplussed when my dog started talking.
* My friend's weird outfit left me completely nonplussed.
* When I told my mom I was dropping out of college, she was nonplussed.
With a specific emotion:
* The news left her nonplussed and slightly bewildered.
* He was nonplussed, but mostly just annoyed by her constant questions.
* They were nonplussed and unsure of how to proceed.
With a humorous tone:
* The cat, nonplussed by the dog's sudden enthusiasm, calmly continued grooming itself.
* I was so nonplussed by the offer of a free pony that I just said, "Sure, why not?"
Remember: "Nonplussed" means confused and unsure how to react, often due to something unexpected or surprising. It's not a negative emotion, but it's not necessarily a positive one either.