Revealing mistake: In the shot in Sarah Jane's attic right after Ruby is thrown into the sun, the group are talking in the attic and to the left of the screen, you can see that the blue screen used to create Mr Smith is visible.
Continuity mistake: The baby carrier little Sky is in as the group heads towards the car changes between takes. When they are walking down the driveway, it is open, and Sarah Jane quickly closes it when Gita comes up. Gita opens the carrier, to discover the baby, and Sarah Jane closes it again. There is more dialogue and Gita goes back to cooing at the baby. When did the carrier open again? Then the car alarms go off and if you look closely, you can see it's closed again, which is confirmed when the baby is handed off to Clyde.