All too often...
I once woke up in a front garden wearing a hideous pink taffeta ballgown and very smudged mascara - coupled with a pair of hobnailed work boots that I did actually own. Very odd, that - and perhaps not surprisingly that my then landlords where I was staying while at college thought it best that I leave.
Then there was...
No; better not to go there.
And then there was the lovely moment when I woke up naked in a deckchair facing east on a roof top in Brixton, just as the sun was rising. It wasn't so lovely for my friend's flatmate, however, who had come in long after I'd headed roofwards in my naked and beatifically intoxicated state, and whose bedroom provided the only access to the roof. It was a rude awakening for the poor lass, but she kept her cool as a hungover naked ape appeared on her windowsill at sparrowfart on a summer's morn.
And I'm sure I can't be alone among Londoners in having that "Oh crap - am I north or south of the river?" moment on waking. (For non-Londoners I should explain - north of the river you're rarely more than a 20-minute walk from a tube station; south of the river there are vast tracts where the underground doesn't go). And as for strange wallpaper, the whereabouts of other people's lavatories and odd pets...
Aye, getting older, wiser and more continent does have its advantages.