No they can't. I don't doubt that this has happened before and I'm sure someone can dig up an example or two.
However, what you describe is highly questionable and borderline illegal. It's certainly grounds for a lawsuit by other shareholders (including options holders).
Eh, this is exactly what happened to a friend of mine. The rationale later, was he had been promised X percent, but when the final deal went through, they diluted different pools of company stock to different percentages, and his values went down to 1/10 what he was expecting.
I know I'm missing a lot of info, and its just a second hand example, but it seems in line with grand parent post's idea that for each type of financial tool, there's at least one gotcha you need to be aware of.
Yes, they can. The board has discretion over the allocation of the options pool that will have been set aside as part of each round.
However to issue those to yourself would be like eating your seed stock, since that's the pool that you use for issuing options to new hires, and without that you can't give new employees any equity. For that reason I don't think it's likely.
I think what the grandparent comment is getting at is that you as an employee have little control over the delayed compensation strategy. If you're lucky, you have a honest founder and investors who make sure you're paid for your contribution at deal closing time. If you're not lucky, you have a board/CEO/founder that will take whatever they can get away with (e.g. your value add) and then point to the financial rules/contingencies and say, "Well, we tried to do all we could, but we had to do this to ensure the success of the company. We needed to compensate the administration because it's hard to find such good talent like ourselves. Your still getting something here..." Or some such line. And you end up with some minuscule share at the same time providing critical value to the business.
founders, angels, and early round VCs can simply issue themselves more stock from the pool of unissued shares to counteract dilution.