Name the only NFL team to play in the Super Bowl as an AFL (pre-merger)/AFC team and as an NFL (pre-merger)/NFC team.

Baltimore Colts.

While both the Colts and the Steelers (and less notably, the Cleveland Browns) were assigned to the newly formed AFC in the NFL-AFL merger, the Colts were the last NFL team to play in the Super Bowl before the merger and were also the first AFC team to play in the Super Bowl afterwards.

The Steelers have played in all of their Super Bowls after the NFL-AFL merger.

The Cowboys have always been in the NFL/NFC.

The Seattle Seahawks are the only team in the NFL that has played in both conferences after the NFL-AFL merger realignment in 1970. In 1976, the Seahawks, along with the Tampa Bay Buccaneers were the first expansion teams to play in the NFL after the merger. The Seahawks were admitted to the NFC along with the Bucs, but were shifted to the AFC following the initial season. In order to create balanced, regional divisions, the Seahawks were shifted back to the NFC in 2002. They have only played in the Super Bowl in the NFC.