spark outside the engine,94 ford expl

Hi everyone:
Happy holidays to all.
I just bought a 1994 ford explorer, did a regular maintenance because i did not know how well was taking care of,i changed the spark plugs, but for some reason #2 spark plug keep firing some spark outside the engine, i kept taking it of and on to see if maybe i didn't line it right, it kept doing the same thing. Any idea why?
Thanks to all.

Maybe a cracked plug or bad wire

Maybe a cracked plug or bad wire
Thanks a lot, yes it was a cracked plug.