I remember the day I started a new position in the company I was working for the same day that they switched to SAP. That was memorable. I've probably posted about it before, but the call center SAP was different to ours, and they'd not enabled the ability to send messages or any other kind of communication between people between the modules (if that is what they were called) so when an order came through for a product that was out of stock (or unavailable -- we were in a place where during a major sale, so much stuff came into the dock that anything behind and above it on a pallet was inaccessible for days sometimes) we had to write out the details on a piece of paper and then fax it to the call centre.
One of the best bits was that it had to integrate with the point of sale system, which was ancient, and DOS based. It didn't really integrate of course, but all the store systems would upload all the sales data at 10pm every night, after closing. Since our delivery centre at the time was attached to a store, and our stock also part of theirs, we ended up doing a lot of faxing! One day though, one of the young kids found a bug in the POS system, and proceeded to demonstrate it to everyone, including the managers. That was fine...until the end-of-day sync, when it locked up not only the sync for that store, but every store in the country, resulting in managers turning up in the morning to find that they didn't have a working POS system and all sales had to be done manually.