Just reading this last week. It's an Irish story, written down in a 16th century manuscript, but may predate it by a few hundred years, about a legendary king, Fergus mac Léide, and his encounters with a Leprechaun king and his wife. The original translation by Standish Hayes O'Grady glosses over the incident, and I think by reading it, you'll guess why. The Irish is quite simple, and could be easily updated to modern Irish by changing a few spellings.
ocus is mé as rí orra sin ocus Iubdán
m'ainm . ocus ben dam an ben úd atchi'thíse im fochair . ocus is
í as baintigerna ar thuathaib luchra ocus Bé bó a hainm . ocus ní
dubartsa brég riam ar Iubdán. aspert Fergus : berar sút imach i
gcenn in gairbteglaig ocus coimétaidh co maith é. rugad Iubdán
immach iarum ocus ro fágbad Bé bó istig i fochair Fergusa ocus
tuc Fergus grád dermhár di ocus do comriacht ria. ocus in uair
ro búi Fergus ic comriachtain ria tug lám ar mullach a cinn ocus
ro fhiarfaig in rigan de cid imar chuir in lám ar a bathais.
ingnam lium ar sé in ball ferrda ina bfuilit secht nduirn ocus gan
innatsa acht trí duirn gan a dhul trét chen sechtair . ocus is
uime sin do chuires mo lám ar do chenn. léig as alé a Ferguis ar
sí : is mór ní súigios lesrach banscaile. (Silva Gadelica p. 244.)
'And I am king over them and Iubhdán is my name. And my wife is that woman that you see in my company. And she is queen over the tribes of the luchra (i.e. wee folk) and Bé Bó is her name. And I have never told a lie, said Iubhdán'. Fergus said 'Take him outside amongst the rough household.' Iubhdán was then taken out and Bé Bó was left inside in Fergus's company and Fergus professed tremendous love for her, and he made love to her. And when Fergus was making love to her, he placed a hand on the top of her head, and the queen asking him for what reason did he place the hand on the crown of her head. 'It's a wonder to me that my penis, which is seven fists long, and you only three fists long, hasn't come out through your head. And it's for that reason I placed my hand on your head. 'Ara cop on Fergus' she said: 'A woman's thighs can absorb a lot'.
I'm into smaller guys. It's not a sexual preference really, I just find they don't need as much rohypnol. ;)