Recieved paychecks after termination?

I was terminated from my job and a little over 2 months later i received 3 paychecks in the mail, after already knowing I had retrieved them all before I left the place. The actual pay is for 0 dollars and 0 cents on all three and they all say I worked 0 hours but was payed for " incentive-reimbursed." It is less than $20 total, but I was taxed for this, AND they deducted union 132 dues from me. I am now wondering if this is something I should be concerned about when it comes time to file taxes. I'm also wondering why union dues were taken out, as I paid them weekly. I was fired in November, and all checks are for pay periods in December. It is now January. Please help, I would like to know what I should do about this.