The "Pension plan" box in the list of uncommon situations says "I got money from a nonqualified pension plan (such as a 457)." You would check that box if the income on the W-2 is a distribution from your 457(b) plan. I don't think that's your situation. If you are not retired and the W-2 is for your current wages you do not check that box. Having money deducted from your pay and put into the 457(b) is not the uncommon situation that that box is for.
As rjs suggests, your governmental 457(b) plan is a a qualified retirement plan that would report distributions on From 1099-R, not Form W-2, so you should answer No to the list of uncommon situations.