[Update: Valve has denied the rumour]
Reports have emerged today claiming that Apple CEO Tim Cook has been seen at Valve's offices in Seattle.
Valve already gave the rumor mill a turn today by posting a job listing for hardware engineers.
Now, the sighting of the CEO of the most valuable company in the U.S. has lead to even more speculation, with rumours ranging from the tame suggestion of "increased collaboration," to the grandiose assertion that Apple is planning to buy Valve.
Though the rumor, first reported by Apple Insider, has not been confirmed, there are already several examples of collaboration between the companies.
In 2010, Valve launched Steam for Mac, and has since made numerous games available for Apple computers through the digital download service.
This year, Valve expanded the Steam network yet again, releasing it for iOS and Android devices, enabling users to keep track of and chat with their Steam friends on the go.
Since the launch of the iPhone, Apple has become a major player in the gaming industry, reportedly drawing as much as $5.4 million a day from the app store in January.