Born in the Bronx, New York, Kranepool attended James Monroe High School, where he began playing baseball and basketball.

After batting a combined .301 at three levels of the Mets' minor league system in 1962, Kranepool received a September call-up in just his first professional season.

He made his major league debut wearing number 21 on September 22, 1962, as a late inning defensive replacement for Gil Hodges at first base in a 9–2 loss to the Chicago Cubs at the Polo Grounds.

[2] Kranepool began the 1963 season splitting playing time with "Marvelous" Marv Throneberry at first base and Duke Snider in right field.

Tim Harkness was awarded the first base job, with Snider shifting to left field and Kranepool becoming the Mets' everyday right fielder.

With Harkness, Dick Smith, and Frank Thomas sharing first base, Kranepool received most of his playing time in right field at the start of the 1964 season.

Kranepool played just 15 games with the Bisons, hitting three home runs and batting .352 to earn a promotion back to the Mets.

"I wish we could have played another 40 minutes", Kranepool was later quoted as saying of the record setting double header that lasted nearly 10 hours and ended at 11:20 PM.

Prior to the start of the 1965 season, the Mets acquired future Hall of fame pitcher Warren Spahn from the Milwaukee Braves.

Kranepool was reportedly part of proposed a trade package along with Amos Otis and Bob Heise when the Mets attempted to acquire the Braves' Joe Torre who went to the St. Louis Cardinals for Orlando Cepeda instead.

This was followed by a five-game losing streak that saw the Mets fall into fourth place in the newly aligned National League East.

On July 8, Kranepool hit a fifth-inning home run off Ferguson Jenkins to give the Mets a 1–0 lead over the Cubs.

[8] The Mets completed their remarkable "Miracle" 1969 season, in which the team, backed by Kranepool, Tom Seaver, and Jerry Koosman, won their first World Series title against the Baltimore Orioles.

The late-career demotion marked a turning point for Kranepool, with him becoming a useful hitter and first baseman/outfielder despite never entering a season with a specific full-time role.

Kranepool still managed to play 100 games and make 320 plate appearances backing up Milner at first and Cleon Jones in left.

Charles delegated his authority to his three daughters, who left control of baseball matters to club chairman M. Donald Grant.

Kranepool, perhaps as a symbol of the Mets' past glory, emerged as a fan favorite as well, despite his relegation to a limited pinch hitting role at that point in his career.

The ad showed Kranepool in front of a mirror, lathering up and shaving, and switched to color footage of him hitting a ball down the right-field line.

As baseball players had long had a reputation for being superstitious, the ad closed with Kranepool standing in the dugout, in uniform but lathered up and holding up a can of Foamy, saying, "I don't know, but now I shave every other inning."

The ad was clearly inspired by the New York blackout of the previous season, which came during a Mets home game at Shea Stadium on July 13, 1977.

Kranepool also appeared on Saturday Night Live in a cameo appearance, being interviewed by Bill Murray during a skit filmed during spring training in 1979, regarding Chico Escuela's (portrayed by Garrett Morris) tell all book, Bad Stuff 'bout The Mets (a parody of Sparky Lyle's tell all book about the New York Yankees, The Bronx Zoo).