Off topic a bit, but, as the guys with orange shirts are here, I'll ask anyway.
The EGGW -> LEMG flight yesterday (Sunday) lunchtime returned to EGGW a bit sharpish with a cargo door warning light on. Its FPL said it was a 737-300. Fairly soon afterwards the flight departed again with a new FPL stating it was a 737-700.
Incredibly fast aircraft swap, or slip of the pen on the FPL? No big deal, just nosy.