If I accidentally entered my wife's data instead of mine, is it very wrong?? Just to clarify, we work at the same place, but the earnings differ by $20 for the period.

It's wrong enough that, if you haven't filed your return yet, you should go back and correct your entries.

However, it's probably not wrong enough that you need to file an amended return, if you've already filed.  For example, was the mis-identifying information only on Form W-2 information you entered, or was it elsewhere on the return?  If it's just W-2 info, you're probably fine.  If you provide more information, we might be able to provide a more thorough answer.