In my case in was my mum who went utterly mental. There's only me and her, so she was doing the Father of the Bride stuff as well - walking me down the aisle, giving a speech, etc.
DH and I decided on a location for our wedding which was reasonably convenient for everyone invited - majority of the guests coming from London and Newcastle. Mum lives in Devon. No one else did, and it's not a place which holds any significance to me or DH - she moved there when I was at uni, so it had never been "home" to me.
She threw an absolute screaming temper tantrum when we told her. Said it was "unforgivable", that the bride should be married from her parents' home as it was "tradition" (she'd never bothered marrying herself so why she was so suddenly hung up on tradition I don't know!) and that if we didn't get married near her she "wouldn't get to do anything!" I pointed out that was doing both MOB and FOB roles, to which she replied "yes and that's all I'll get to do!" I asked her how much more she expected to do, and if she actually realised it was me getting married and not her.
This went on for a while, till I eventually told her that if she didn't stop behaving like that, we'd elope and no one would get to "do" anything, and hung up on her. I then refused to take her increasingly abusive and angry calls for a couple of weeks, till she seemed to calm down and apologised.
A few months before our wedding, the venue we'd booked cancelled on us. They said they had to have some building work done over that period - which was very odd, why would a wedding venue chose July to close down for building work. This was a bit of a disaster as we'd booked and paid for quite a lot of stuff by then, and the MOH and BM had booked their flights from different continents to be there on that date.
I rang mum in tears, and she said not to worry, there was a beautiful venue ten minutes down the road from her that had availability ten minutes down the road from her...
It actually was a beautiful venue, and we needed somewhere, so we went ahead with the wedding there, and it was a wonderful day. But over ten years later I still wonder how mum pulled that off - and also what made her behave that way in the first place.