To the untrained eye a serial port and VGA port do look similar.
Kids these days.
I hate it when these kids unintentionally mock my childhood stuff.
Centronics for example is such a beautiful word, I would die to have it back.
As a teenager, I once plugged a 9-pin VGA monitor into a 9-pin serial port. The computer turned on, did beeps and boops for a few seconds, and then white smoke started pouring out of the power supply. I quickly turned it off. After it cooled down; I connected it he monitor to the correct port and the computer fired up just fine.
VGA use a 15 pin DSUB connector though.
You're right. It was a CGA monitor. Forgot that detail.