Continuity mistake: When Julie passes through the kitchen to get Malcolm, Dewey and Egg are in there cleaning the floor they have suds all over the floor, When Julie runs back through after seeing Malcolm in his underwear she slides across the floor, The floor is still completely covered in suds but when she gets up if you look in the background you see the floor with hardly any suds anywhere. She could not have soaked up all the suds when she slid across.
Continuity mistake: When Lois is in the bath tub soaking after getting upset about the family wanting to go to the funeral. Dewey comes in and ask for juice. When they are on Lois(front view) the suds barely come to the top of her breast. When the show Dewey (side view of Lois) The suds are all the way up to her shoulder.
Continuity mistake: When Lois is packing lunch in the blue cooler her hands go from on the side of the cooler to down by her waist in one frame to the next. No time for her to move it.
Continuity mistake: When we see Dewey's friend at the table eating cereal he is eating cereal and the bowl is full of milk. In the next shot the bowl is full of cereal and there is barely any milk.
Answer: It is made up - although it is implied she is Croatian, she never mentions it herself.