Can my employer require me to get a doctor's note? Part-Time Worker

Well, it depends on how many sick days in a row you took -- more than three? Are you under a union collective bargaining agreement? What does your work employee handbook say.  Unfortunately, as a part-time employee, you really don't have many of the same protections full time employees do.

In terms of employment law, check out the following:

http://dwd.wisconsin.gov/er/discrimination_civil_rights/fair_employment_law.htm

The Wisconsin Department of Workforce Development should be able to help you further.

I am a lawyer in CT, not WI, but i have helped clents in a similar situation.  Were you issued an employee handbook when you were hired?  Does one exist? If so, read it to see if there is such a requirment.  Were there any notices at work implementing such a rule?  I would need to know the answers to these questions to help you. The employer basically thinks that you played "hookie" and wants proof.  I guess you were sick but didnt go to see a doctor.  That is very easily explained to the employer.  Why wont he/she accept that?  What kind of discipline are you receiving?  In any event, it doesnt sound like you are being treated fairly.  However, you are an at will employee, meaning that you can be fired for good bad or no reason at all.  You want to be careful based on what you tell me about the employer giving bad recommendations.  Get me the answers to these q's and write another question posting asking JMA for a response.