When Maggie is describing Bob's proposal, she refers to being at an "Oriole" game. When people use the actual name of Baltimore's Major League Baseball team, they always refer to the "Orioles." (The team's nicknames are the "O's" or the "Birds.")
Maggie presents Ike with a gift of the 'Miles Davis' album "Kind of Blue." The closeup shot is that of the original 1950's album cover. The camera cuts to a shot of the two of them in the doorway, and the album cover has changed to the "Columbia Jazz Masters" reissue cover from much later.
When Ike comes into Curl Up And Dye for the first time, Maggie calls Peggy over and points to the counter at the article with Ike's picture (and the devil horns and pitch fork that has been added on). It is originally on taped on the counter, but in the next shot is taped onto the mirror.
At the baseball game, when Ike first comes up to Maggie and Peggy's row, behind and to the right of them is a blond-haired woman talking every so often to a black guy. Halfway through the scene, there is a different black guy talking to the same blond-haired woman (although he is wearing the same clothes as the other one).
During one of Maggie's wedding videos that Ike is watching, we see Maggie running away from the altar with the ring bearer (a young boy) being dragged behind her by holding onto the train of her wedding gown. The video he watches has points of view that would suggest at times the bride is holding the video camera and pointing at the boy being dragged, and it shows another point of view as if the little boy is holding the video camera and videotaping the bride running out of the church.
During her first wedding with Ike, Maggie leaves the church through an open window in the day care center. On the window sill and spread out onto the grass is a sheet, as if to protect her wedding gown. There is no other reason for it to be there.