Parker Ballantine is a New York theater critic and his wife writes a play that may or may not be very good. Now Parker must either get out of reviewing the play or cause the breakup of his marriage.

Story follows the rise and subsequent fall of the notorious head of a New York crime family, who decides to testify against his pals in order to avoid being killed by his fellow cohorts.

When the Lemon Drop Kid accidentally cheats gangster Moose Moran out of his track winnings, the Kid promises to repay Moose the money by Christmas. Creating a fake charity for "Apple Annie" Nellie Thursday, the Kid tricks his gang into donning Santa suits and "collecting dough for old dolls" like Nellie who have nowhere to live.

Larry Nelson, paroled from prison after serving nearly half of his thirty-year sentence, is determined to not fall into the clutches of the law again, and takes a quiet job at a country sanitarium. Thete, he meets and falls for a nurse, Charlotte Maynard, and he knows the only way to enter her web is to have a lot of money, for Miss Maynard is somewhat of a gold-digger. There is a $1,000,000 robbery of an armored car, and one of the robbery gang turns up at the sanitarium. So Nelson works a money-making, shady deal with an inmate, but soon finds himself a clay pigeon for other members of the gang. Meanwhile,sweet-and-wholesome nurse, Ann Taylor, is doing her best to make Larry see he needs to take another direction.

An unscrupulous boxer fights his way to the top, but eventually alienates all of the people who helped him on the way up.

About the only thing kept in this film from Preston Sturges origianl story for "The Miracle of Morgan's Creek" is a girl that gets drunk, gets married, gets pregnant and doesn't even remember any of it. A major dirrerence is that "The Miracle of Morgan's Creek" was a classic comedy and "Rock-a-Bye Baby" isn't. This time out, Clayton Poole (Jerry Lewis) is a small town TV repairman who is still in love with his former hometown sweetheart, Carla Naples (Marilyn Maxwell), who is now a famous movie queen. When Carla becomes pregnant due to a hasty marriage in Mexico, which she has forgotten about, the studio tells her a baby will ruin her career so she turns to Clayton, the only person she can trust, and he agrees to care for the baby when it is born. Carla gives birth to triplets and Clayton finds he must get married before he can adopt them. He marries Sandy (Connie Stevens), Carla's younger sister who has always loved him. The press learns about Carla's triplets and she tells reporters she is secretly married to Clayton. Clayton, having rapidly gone from no wife and kids to two wives and three kids, goes into hiding. He returns after several months---nine to be exact for those old biddies who are counting---and learns that Sandy has given birth to quintuplets.