Installed 555 timer socket backwards - can I reverse the chip in the socket?
The real question is why you'd use a socket for a cheap IC like a 666 555 timer, or why you'd even use a thru hole part in the first place, but I digress.

OK, closing my eyes and trying to imagine back to the Pleistocene.

It depends on what you mean by "backwards".  If you simply started counting pin 1 in the wrong corner, then all you have to do is rotate the chip.

If you actually mirror-imaged the footprint, it can still be done, although it's a bit more tricky.  Basically, you bend all the legs 180&deg;.  That's conceptually easy, but the trick is to not break them off in the process.  Do it right so you only need to bend them once.  Use a flat screw driver or something to bend each leg the other way right where it comes out of the package.

It's probably a good idea to somehow mark the pin 1 corner on what used to be the bottom of the chip but is now the top.  That avoids the next thing you'll do wrong, which is to plug in the flipped chip rotated.

Another trick for a mirrored footprint is to mount the unmodified chip on the bottom of the board instead of the top.

Back to your regularly scheduled time and place.