My employer has a steadfast rule forbidding overtime. It's to the point that if you go one minute over, HR gets an email from the main office and you get pulled in by a manager to talk about time management.

But the holidays are busy and everybody is running around like crazy. We are short staffed in some areas. Those of us who have been there long enough to be paid for the holiday are only allowed to work 32 hrs so the holiday pay does not put us over 40 paid hours.

I was asked if I could cover another shift, as any hours actually worked up to 40 are fine. Holiday pay does not calculate into overtime. During the extra shift, I found out that managers are allowing everybody who wants extra shifts to work as much as they want. Once you say you want an extra shift, all attendance policies apply including but not limited to calling in and risking holiday pay for not showing up. I asked a manager, we went over my schedule and my availability and I added 17 hours on top of my full time hours.

But now I'm finding out that alot of my coworkers are refusing to work extra hours because OT is being paid at our regular hourly rate rather than time and a half. Is this legal? I'd prefer the extra hours either way, but I would like to be paid reasonably considering I've already put in my first 12 hour day and I expect another (with more hours added to the 17 extra) to come. The week is not finished and I may talk to my managers about going home early a couple days to be with the kids if I'm not getting paid extra to be there.

Many of my coworkers are saying they've worked overtime at points this year and not been paid for it. I've worked overtime as well at points this year and I have been paid for it. Is there a reason I would be while they would not be?

I've worked overtime as well at points this year and I have been paid for it. Is there a reason I would be while they would not be?

Sure, why not.

Not all workers are legally "employees", and there is no legal requirement that non-employees be paid overtime.
http://payroll-taxes.com/articles/art2.html

There is a federal law called FLSA which is where the overtime rules come from. However not all empoyees and employers are subject to FLSA.
http://www.dol.gov/esa/regs/compliance/whd/whdfs14.htm

Even if the employee and employer is subject to FLSA (almost all are), certain classes of employees are Exempt from paid overtime based on the nature of the work they do.
http://www.dol.gov/esa/regs/compliance/whd/fairpay/main.htm

Certain industries have exceptions specific to their industry. For example, an automobile mechanic working for an automobile dealer is not legally eligible for overtime premium while an automobile mechanic doing exactly the same work for a garage would be eligible for the overtime premium.
http://www.dol.gov/esa/fact-sheets-index.htm

Assuming that the employee is legally eligible for an overtime premium, that is only legally applicable to hours actually worked past 40 in the work week. You mentioned holiday pay. Paid time off (holiday, vacation, sick, whatever) has nothing to do with the overtime calcuation. Many employees who work extra time during the holidays want that extra time paid at a premium rate even though they are not actually working more then 40 hours in the work week. That is not what the law requires.
http://www.dol.gov/esa/regs/compliance/whd/whdfs23.htm

And of course, there is always the possibility that your employer either does not know what they are doing or is deliberately breaking the law.

Many of my coworkers are saying they've worked overtime at points this year and not been paid for it. I've worked overtime as well at points this year and I have been paid for it. Is there a reason I would be while they would not be?

My guess would be that they did not actually work more than 40 hours a week. They may have worked 40 and had a paid holiday, but that does not grant them overtime, as you recognized in your post (thank you for that). There could be other explanations, too.

I am not sure what your issue is.

If you fear that agreeing to work overtime will result in you being paid straight time based upon some comments by others, I would suggest working the time, if offered and if acceptable to you (not always a choice) AND, if the employer does not pay the amount due, talk to HR and/or file a wage complaint.