In the movie, Another Earth, Rhoda told John that Yuri Gagarin heard a ticking sound during his journey into outer space. He couldn't find the source, and eventually came to love that ticking sound.
Did this really happen to Yuri Gagarin?
I've seen this story a number of times since Another Earth was released in 2011, usually something along lines like this article.
The problem is that I've never seen anything about it in any of the official histories or biographies of Gagarin. Also, the stories all seem to think Gagarin's mission was to last 25 (or 28 depending on the story) days.
In fact, the flight of Vostok 1 was only a single orbit and took only 108 minutes from launch to landing. Not much time to spend searching for a "ticking sound"!
Vostok 1 was Gagarin's only spaceflight (although he served as backup crew for the Soyuz 1 mission), so I think that the stories are based on the movie, rather than the line from the movie being based on actual events.
I asked an expert on Gagarin to review the question:
"I never heard the story about unexplained ticking, but I do know that he wore Sergei Korolev's wrist watch. At least that is the Russian legend." Personal correspondence with Cathleen Lewis, curator in the Division of Space History, Smithsonian National Air and Space Museum
She notes she has not seen the movie referenced in the question.
The cabin was pressurized (Gagarin reported "cabin pressure 1" at several times - although he specifies no unit, it is safe to assume that he used the same unit as for other pressure measurement, which was the "atmosphere"). So he could have sounds travelling though the air.
As this was his own personal watch which has been wearing for quite some time on Earth, he might have gotten attached to that sound. However, he probably wouldn't have had to guess about the source of the ticking in that case.