I've been through two Workday loops myself and coached four people through theirs over the past year. Here's a consolidated take on the behavioral component.
Workday has what they call their Core Values: Employees, Customer Service, Innovation, Integrity, Fun, and Profitability. Worth knowing the list. They don't always tell you they're mapping to them but you can feel it in the questions.
Most common behavioral themes I've seen: A time you had to work with a difficult stakeholder or cross-functional partner. (Integrity + customer service.) A time you disagreed with a decision made by leadership. What did you do? (They're really asking: can you advocate without being a problem?) Tell me about a project that didn't go as planned. What happened and what changed? (They care a lot about ownership and not throwing teammates under the bus.) A time you had to learn something new quickly to solve a problem. (Especially relevant if you're coming from outside enterprise / HCM domain.) Describe how you've handled competing priorities on your team. (Weighted toward senior/staff levels.)
Structure your answers STAR but don't be robotic about it. The interviewers at Workday tend to probe. They'll interrupt and ask 'and then what did you do?' or 'how did that person respond?' so have depth on your stories, not just the surface arc.
The 'fun' value is real by the way. They have an actual culture question in some loops, often framed as 'how do you contribute to team culture' or 'tell me about a time you made your team better as a place to work.' Don't dismiss it. It's not a softball.
One thing I noticed: Workday interviewers react well when candidates have done some homework on what Workday's actual customers experience. Not product knowledge, just empathy for the stakes: HR admins, payroll professionals, employees waiting for their paychecks. Shows you understand the domain before you walk in.