I have had the same problem with my 2003 TJ. I was going up a hill in 5th gear talking to the wife, should have down shifted but hadn't yet, just mashed harder on the gas peddle. then the check engine light came on. It was also a #1 cylinder misfire. I did not change the sparkplug, I just reset the computer. it's been 7-8 months now with no problem. I wrote it off as an computer (or software) glitch. When is your light coming on, is it during a heavy load on the engine? When you change your plug is it actually fouled? I have an OBDII scanner and when I hook it up to my Chevy Tahoe it gives me a count of how many times each cylinder has misfired. The point is misfires are not a problem... too many misfires are a problem. Who knows what the algorithm is that the Jeep computer is using to turn on the check engine light for misfires. If it happens again (if I were you) I would try an experiment. I would just reset the computer and see how long it takes to get check engine light again.
Well, good luck keep us posted...Thanks,