I want to ask out my coworker
Why? Do you have a crush on her?
Nah. Asking her out is just a prank I will pull on her.
I think it would be mean to play a prank on her to ask her out, she should get the wrong expression. It's expected that workplaces will maintain a level of professionalism. It might not be a good idea to date one another.
I'm going to do it anyway.
Then you should be prepared for awkwardness and possibly termination from your job. Your workplace should be strictly professional, not a place to pull pranks.