Here's the full list:
Allie Clark (1947 Yankees, '48 Indians)
Clark recorded just two World Series at-bats for the Yankees in '47 and three the following year with the Indians after being traded in the offseason for Red Embree. But despite his minimal contributions, Clark became the first player in recorded history to win consecutive titles in different uniforms.
Clem Labine (1959 Dodgers, '60 Pirates)
Best known for his exploits in the early to mid-1950s, Labine was at the tail end of his career when he won the '59 World Series with Los Angeles. He threw only one inning in the Fall Classic against the White Sox before struggling for the Dodgers to start the '60 campaign. Labine was then dealt to the Tigers, who released him by mid-August. That's when he turned around his season by signing with the Pirates. Labine went 3-0 with a 1.48 ERA, helping Pittsburgh win the pennant -- although he struggled in the Fall Classic, allowing six earned runs in four relief innings.
Moose Skowron (1962 Yankees, '63 Dodgers)
Skowron's career followed a similar path to that of Labine. After a long, successful tenure with the Yankees, Skowron was traded following the '62 season, during which he won his fourth championship. He struggled in '63 with the Dodgers, but perhaps his familiarity with the Yankees paid off, as he hit .385 with a home run in the World Series against them.
Don Gullett (1976 Reds, '77 Yankees)
A staple of winning ballclubs during the '70s, Gullett twice led his league in winning percentage. He allowed a run on five hits in a Game 1 victory for the Reds over the Yankees in 1976, only to sign with New York as a free agent in the offseason. A year later, Gullett started two games in the World Series against the Dodgers, including an eight-inning, two-run effort in Game 1.
Jack Morris (1991 Twins, '92 Blue Jays)
Morris' Game 7 gem against Atlanta in '91 is arguably one of the greatest games ever pitched. He followed that 10-inning, World Series-winning shutout by signing with the Blue Jays that December. Morris led the American League in wins in '92, but his World Series numbers that year weren't quite up to his incredibly high October standards. He took both of Toronto's losses in the series, allowing 10 earned runs in 10 2/3 innings, but the Blue Jays were still able to knock off the Braves in six.
Ryan Theriot (2011 Cardinals, '12 Giants)
Theriot hit just .077 in the '11 Fall Classic against the Rangers, but he nonetheless played a pivotal role on that Cardinals team as a utility infielder. In the ensuing offseason, Theriot signed a contract with the Giants and once again reached the World Series, this time at the expense of the Cards, whom the Giants beat in seven games in the NLCS. Theriot had just one hit in the '12 World Series against the Tigers, but it was a vital one. He led off the 10th inning in Game 4 with a single and scored the winning run on Marco Scutaro's RBI hit, and the Giants completed their sweep.