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When two people kiss, they form a long tube from one anus to the other
(self.showerthoughts)
A "Showerthought" is a simple term used to describe the thoughts that pop into your head while you're doing everyday things like taking a shower, driving, or just daydreaming. The best ones are thoughts that many people can relate to and they find something funny or interesting in regular stuff.
From an evolutionary standpoint, yeah, we're donuts or tubes. It was either that or cups. Those creatures, like sea anemones eat and expel, erm, waste out of the same hole.
An example of a fellow tube is a sea cucumber