In 5.08 Changing Channels, Gabriel traps Sam and Dean in a series of TV shows. The final one is Knight Rider, a 1980s series about crime fighter Michael Knight, played by David Hasselhoff, and his intelligent car KITT.
On a psychological level, this "trick" of Gabriel's has some sexual subtext that the producers are very likely aware of: Sam and the Impala, both very high up in Dean's affection, become one being. When Dean roots around in the Impala's trunk looking for holy oil, Sam complains that what Dean is doing is uncomfortable. He then says "ow" when Dean slams the trunk closed. Later, when Gabriel asks where the boys got the holy oil, Dean answers, "You might say we pulled it out of Sam's ass."