Fun times indeed, been there and done that. What I'm paid to do is not IT related but since I'm known to have knowledge of such I get tossed into the SHTF situations since I'm physicially there already. Basically end user plugged ip phone into wall jack and then ran a patch cord from the pc port on the phone to other port of the wall jack. Completely crippled the cisco router acting as primary gateway so brought everything to a halt. Equipment is capable of STP and BPDU but all turned off
When they were running out of available IP addresses instead of segmenting network they just switched to a 16-bit subnet.