Certain of our regular readers have issues with unipeds. Unauthorised investigations of the individual's psyche using the Riddled Dream Machine reveal the roots of the obsession.
It is evidently an ancestral memory that can be traced back to the alien encounter of 1512 that subsequently became known in Ufological circles as the 'Ravenna incident'. As evidence of the potency of this suppressed engram, we note that several centuries after the event it inspired Mr Vitilgo Bracefumble of Eketahuna to invent the first parking meter, or "one-legged bandit" as it was known at the time, on account of this pre-dating legal casinos and on-line gambling so gamblers had to take their fun where they could find it.
In fact the spaceship contained two aliens. According to contemporary broadsheets, the second one "did converse by Fartes and ye Dancing in Tappes"... this was seen in the eyes of the public as a sign of divine displeasure with the corrupt Papacy of Julius II. The two separate entities became confused in eyewitness accounts and in popular memory, which is why the Dream Machine display differs in so many respects from an accurate description of a Tralmafadorian.
Eyewitness testimony is notoriously unreliable, as I was saying to the court just the other day.
UPDATED with bonus farting & tapdancing.