Continuity mistake: Lois is wearing shoes and socks when Malcolm and Reese go running past her and Hal to the Liquidator. Then, when she, Malcolm, and Reese come flying out of the ride, she’s suddenly barefoot.
Visible crew/equipment: After the theme song ends it starts with Lois just finishing shaving Hal's back. Off to the side you can see the crew kneeling down.
Continuity mistake: While Dewey stands on the table, Mrs. White (Bea Arthur) dips her finger in the bowl of chocolate and draws a mustache with it on Dewey. In the following shots the chocolate on Dewey's face differs.
Continuity mistake: When Malcolm and Reese talk about April at the water park, there's a girl with a blue shirt and a towel tied around the pelvis who passes behind Malcolm twice in two different shots.
Visible crew/equipment: You can see the crew right after the intro. (00:01:00)
Answer: It is made up - although it is implied she is Croatian, she never mentions it herself.