D.W. is 4 years old, but her parents put her in time-out in her room for 10 minutes. Normally, time-outs when disciplining kids is 1 minute per the kid's age. If she's 4 years old, she should be in time-out for 4 minutes, not 10.
D.W. recalls Lucy's wedding and refers to her as "Cousin Lucy." When she was first put in her room, she mentioned "Aunt Lucy," which is the correct relationship.
When Arthur doesn't want to wear the polka-dot bow tie, he says that James Hound's bow tie is black. However, the movie trailer for James Hound showed him wearing a red bow tie.
In one of D.W.'s flashbacks, she tries add the Princess Sneeze-and-Wet doll into the shopping cart while shopping with her mom and sister Baby Kate, which her mom orders her to put it back where she found it. D.W. already had this doll in the earlier episode "D.W., the Copycat".
In D.W.'s fabricated flashback claiming she didn't go to her Aunt Lucy's wedding (which she actually did in the episode "D.W. Thinks Big" as well as the book it was adapted from), Grandma Thora is shown going to the wedding. Grandma Thora did not attend Aunt Lucy's wedding in "D.W. Thinks Big".
D.W. can't tell time and since she doesn't know how to read, she assumes she's been in her room for hours, even though her mom says she has to be in her room for exactly 10 minutes from 4:30 until 4:40 PM. However, D.W.'s imaginary friend Nadine tells her that if the time says 4:31, it means one minute has passed.