Continuity mistake: After Shelby dies, her mother (Sally Field) goes to pick up Jack Jr. While he is running to her, in one scene he has a toy in his hand, the next he doesn't and when Sally Field picks him up, he has it again.

Continuity mistake: In the scene where the women are putting the eggs into the car and Ouiser walks over to Annelle and begins to converse with her, she is holding a carton of the eggs. The two front corners of the eggs keep changing colors as the shots keep changing from Ouiser and Annelle speaking.
Continuity mistake: In the last scene at the easter egg hunt Shirley Mclaine comes in with brown high heel shoes on. When she creeps up behind the tree to sit with Jack she has no shoes on and when she is running after the truck taking Darryl to the hospital she has tennis shoes and white ankle socks.
Continuity mistake: In the scene where Shelby is getting her hair done before her wedding, she begins to have a diabetic attack. Sally Field lifts up the hair dryer she is under...then in the next shot, you can see her lift it again.
Continuity mistake: The Christmas decorations in the outside of the house change as to where they are and what they are.
Revealing mistake: When Truvy is blow-drying Shelby's hair after she's cut it short, you can tell the blow dryer is not really turned on. The sound was obviously added in later at a lower volume so the characters could talk comfortably over it. Dolly Parton is running her fingers through Julia Roberts' hair to hide the evidence, but if you look closely, you'll see that none of the hair is actually being blown. The only hair moving at any given time is the part that Parton is actually touching.
Continuity mistake: Janice van Meter's dress at beginning of the reception is floral with a flowing bottom. Then when when dancing with Trudy's son and looks like "2 pigs fighting" its tight and cream.
Revealing mistake: During the Christmas scene at Truvy's, after Enelle has just finished decorating the outside of the house, she stands on the porch and talks to Shelby and Truvy. We see Clairee in the foreground, her lips moving and her animated, as if she is talking to someone just off camera. (This is a common practice in plays, for example, if we want the audience to hear one conversation, all the other characters will pantomime talking so the conversation can be heard.) So this would be fine - except that there is no one left for Clairee to be talking to. Everyone else has either gone into the house or is on the porch behind her, and Oiser hasn't arrived yet.
Continuity mistake: In the wedding reception dance scene, you see a couple dancing amongst the guests on the dance floor. The female is wearing a seafoam green dress with a large matching bow in her hair. About 2/3 of the way through the song "On the Bayou," you see this same couple run onto the dance floor from off camera to watch the featured dance couple, as if they had never been on the dance floor at all.
Continuity mistake: When M'Lynn and Truvy are sitting in the backyard drinking tea after the funeral, there is no greenery next to where Truvy is sitting. In the next shot, when Clairee and Ouiser walk in the backyard together next to Truvy, there are now bushes and some trees that weren't present in the shot beforehand.
Continuity mistake: In the scene after Shelby's funeral has taken Place where M'Lynn, Truvy and baby Jackson are in the backyard, Annelle is bringing the two ladies some tea. In the next shot, Ouiser and Clairee walk into the backyard and now present in the shot next to Truvy is a small tree and shrubbery that was not there before.
Answer: I believe it is because the child playing Jack Jr. was basically crying through this whole scene, as you can see. It's most likely his (actually her, as the real baby was a girl) real mother holding him to calm him down. Also, when the family is saying "Blow, blow," you can hear a female voice that is neither Julia Roberts or Sally Field.
When she is sitting with Jack Jr, it is before she goes to get her hair cut. When she tells M'Lynn she wants to cut her hair, she is wearing it in a banana clip and you can see the hair past her shoulders. When "she's" sitting with Jack Jr, there's no hair to be seen. Total stand in.
Daniel Camp is the actor who played Jack Jr.
Along with Daniel two other children played Jack Jr, C. Houser and Clara Gabrielle.