After Francine spills coffee on the fake eviction letter, in the first shot in close-up where she's wiping up the mess, she is wearing her casual red shirt. In the next shot when the camera is zoomed out facing her when she stuffs the letter into the envelope, she is wearing her pajamas.
At the start of "Francine Goes to War" after the title card: in the girls' bedroom, their beds are first shown to appear well-made with their pillows at the head ends by the window. When the camera switches back to the angle of their beds after Catherine sharpens her pencil, their beds are sloppily made and the pillows are on the foot ends right before they pick them up to start their pillow-fighting.
When Francine and Muffy prank call Mrs. Pariso, the latter of the girls spills out the former's real name before remembering that she was going by the alias of "Ed" while prank-calling. So really, Mrs. Pariso would already know who Francine is and what she did before meeting for the first time.
Right as Francine and Mrs. Pariso leave the Sugar Bowl, the sign for Banana Royal is misspelled as "Banna Royal".
After Arthur asks Muffy and Buster if any of them should go with Francine, and where Muffy and Buster respond with "No!" and "Mm-mm!" respectively, Buster's mouth movements don't match with the word he says.
In "Francine Goes to War", when Francine and Catherine run out of their bedroom after suspecting a "ghost" due to a banging sound coming from another apartment, Catherine runs out of the bedroom before Francine does, but Catherine has Francine's voice and vice-versa.