Oh, My Aching Antenna - S1-E33
Continuity mistake: Even though Tim and Uncle Martin live on the 2nd floor at Mrs. Brown's above the garage, every view outside the living room window with the sheer drapes shows the house across the street from a ground floor perspective. This happens in multiple episodes.
Spur Line to Shady Rest - S1-E1
Continuity mistake: When the Cannonball is preparing to leave, Uncle Joe has his hat. When the scene cuts to him helping Kate onto the Passenger Car, his hat is suddenly missing and nowhere to be seen.