Wouldn't say our teamwork failed we just sucked that day.

I had a ticket to fix a SQL sp and then correct some data afterwards. As this was the typical "urgent fix need now" we went through a different process for fixing it.

Me: Just sent you some scripts can you check them over before we apply it to uat?
Boss: let's go through it together.
5 mins later
Boss: looks fine I'll apply the scripts.
2 minutes later
Me: did you apply the scripts to uat?
Boss: No I applied them to live.
Me: oh ... oh no.

At this point I realized I was missing a critical where clause so yup my update was applied against all of the data.

Boss: oh
Yup he just spotted my error.

Helpdesk phones start ringing
Boss: you pick it up it's your code
Me: hey you applied its your problem now.

One db restore and several incident meetings later we fixed it. Twas a fun day.