The Mexican house story is stuff of legends! I wouldn't believe it except we had our own cheeky fecker who pushed things over the edge into 'unreal' territory.
Context : When I was pregnant with DS1, we lived in a very small one bed flat in the centre of London. DH and I were working all the hours God sent to save for a deposit on a house.
DH had recently got back in contact with his childhood friend whom he hadn't seen in almost 20 years. His friend lives in France with his wife and DH had been out to see him once but I couldn't go, so had never met them. So one day DH gets a phone call from his friend asking him if his SIL (so the sister of his wife) could come and stay with us for a couple of weeks. She is a lady in her 50's and lives in Algeria. She used to holiday in France with them each year but had been refused a visa because she had tried to apply for an extended visit and they had refused her altogether because they thought she may be planning on staying permanently. She wanted to come to London to sightsee and get away from the summer heat in Algeria. DH told them that we weren't home a lot and she would have to fend for herself and they said that was fine, she just needed a base and she would be no bother.
After consulting me, DH says it's fine and his friend says 'well, actually she might be staying for 3 weeks, is that ok?'. I was a bit 
about this as we really had a very small flat and she would be on the inflatable bed in the living room. I wasn't overly thrilled about having a stranger in my home for that length of time but DH explained that it was customary in his culture to go for extended holidays and it would be costing a lot for her to travel and anyway, she is planning on spending a week up north with a family she knows, so would only be at ours for a couple of weeks. We were hardly there so I thought 'ok, what the hell' - big mistake!
She arrived and very quickly started to get on my tits. I had arranged the weekend off to greet her and spend some time orientating her; showing her how the buses, tube worked getting her travel card set up etc. I had printed off a load of info on different attractions and had expected to just leave her to it but it soon became evident that she was expecting me to look after her the whole time she was there. One thing she would do was sit outside the bathroom door on a morning, waiting for me to come out and as I did she would pounce on me and want me to go over some of the info I had given her. It wouldn't matter if I was dripping wet and in a towel (which I pointed out to her on a number of occasions), she would just say "yes, but if I let you get dressed, you will just go to work". Which was true but was irrelevant because the info that she wanted me to go over was always the same info that we had spent a couple of hours going over the night before. She wouldn't let me watch the telly or chill out, I had to spend my time looking after her as she was "lonely, spending all day on her own and she had thought that I was going to take time off to spend with her" - I don't know you, you loon. I didn't invite you! Bugger off.
She also continually complained about feeling faint because she wouldn't eat until I got in - she expected me to cook for her. I was working really long hours neither DH would be home before 9 most days. We would have eaten whilst out so I had stocked the fridge for her and told her to help herself. I had also cooked some meals and put them in the freezer for her to defrost and eat at will but she refused to do so. She would lecture me on her customs and how the host should cook for and eat with their guests, how as the women, I should make sure I was home to cook for her and my husband 
. At first I would make food for her but in the end I would come home and go straight to bed just to get away from her. Oddly, she managed to start being able to fend for herself.
She was irritating but I just kept thinking "She'll be gone soon" and clenched my teeth.
After a couple of weeks of being with us, it became evident that she was not in fact going up North. When I brought this up with her she told me that she had planned on going to see a family that she used to go and stay with a number of years ago but when she had phoned the man had told her that he couldn't talk right then as they were busy and he would call back - he never called back and they never answered the phone again. She told me that her visits with them had had to stop because the wife had died suddenly and it wasn't appropriate for her to visit alone but that she had heard that the man had remarried so had thought that she could resume visits. DH and I are convinced that the first wife is alive and kicking and it was the only excuse they could find to MAKE HER GO AWAY!
By this time, I was doing my nut. The way she spoke, ate, breathed drove me to distraction but DH wasn't so bothered (probably because she follow him round like a fucking dog). That soon changed though.
I was at work one day and DH phoned me and said "There's a surprise for you when you get home". He wouldn't elaborate and I was hoping that she had packed her bags and gone. This was not the surprise. When I got home there was a French teenager avec luggage in my living room. DH told me that he had had a phonecall mid morning from his friend's Bil asking him to go and pick his son up from the airport. To cut a long story short, this woman had told her sister to send her nephew over to us for the summer. Her sister was having problems with him lazing around and doing nowt so they had decided between them that we could look after him for the summer and DH would find him a job and I would teach him English! Not only that, this woman then threw a hissy fit because we refused to change sleeping arrangements. She was expecting that she would come and sleep in our bed with me (ewewewew) and DH would sleep in the livingroom with the boy. Erm no - you invited him, you sleep with him. She wailed and cried over this but DH stood firm (cos he knew I knew would have divorced him otherwise, she only showered every three or four days and I had pregnancy dog nose). The lad hung around for a couple of weeks eating McDonalds and downloading porn onto our PC. There were many rows but eventually his parents bought him a ticket and he flew home.
She however, was still there. Three weeks had been and gone and I inquired several times about when she was going back but she was very evasive about it. Eventually I got DH to interrogate ask her and we found out that she had changed her ticket so that she would be staying for a total of 9 weeks! 9, aneurysm inducing, weeks!! I went ballistic and told her she had to change it back and she refused saying she couldn't. DH eventually made her do it but she was still going to be staying for another couple of weeks which would in total make her stay just over 6 weeks.
During this time my best friend was getting married and I was to be bridesmaid. She cried for the whole weekend (so she said) because DH and I went to the wedding in Wales without her. She told me she was very offended that I didn't take her and introduce her to my family. Well boo-fucking-hoo fruitcake. Count your blessings cos if I hadn't of had that break, I may well have snapped and throttled your scrawny neck!
In the last few weeks I did my best to avoid being in her company but when I was she would go on and on about how much she loved me, how I was like a daughter to her and how sad her life had been that she had never been married and had children. She kept going on and on about how blessed I was to be having a baby and how she felt like it was her baby too 
. She then started to ask me about weird stuff like 'how would you go about finding a husband in the uk' and could I put up adverts in the local mosque for a husband for her?! When I asked her what the fecking hell she was on about she told me her PLAN. She had decided that she wanted to come and live with us permanently, that I would find her a man to marry to enable her to stay in the country but she would not live with him, she would live with us and look after our baby so that I could go back to work. She saw nothing wrong with this and just kept going on about how lovely it would be for her to finally have 'her own baby to bring up' and how great it would be for us as we wouldn't have to pay her, just give her some spending money and DH could be sure that his child was being brought up properly. .
Yeah, that didn't happen. You'll be surprised to learn that all her subsequent requests for the formal invites she needs for a visa were stoically ignored. I wouldn't even talk to her on the phone for years afterwards especially after I found out that she had manipulated my DH into paying for a credit card bill that she had racked up shopping (which incidentally is all she wanted to do when she was here - she didn't bother going to 90% of the places I had researched for her). It was almost a grand and we were saving hard to get out of the shit hole we were living in, I was beside myself and it took a while for me to forgive DH.
Crazy bitch