A lot of people swear by vinegar, especially if you can get acetic acid, which is a more concentrated form of vinegar, or at the very least pickling vinegar. On regular wood glue. But getting that into the mortise will be pretty tricky. You can cut the leg and then drill holes through the part of the tenon that's left and try to do it that way. Or maybe you'll get lucky and they used hide glue, which should come apart with water and some heat.
I'm quite curious about why you tagged this question as humor?
I'm quite curious about why you tagged this question as humor?