Physics error: Whenever Fiona runs, her cleavage stays in place, but every time Fiona stops running, her cleavage immediately bounces.
Every time a pursuer is injured by Hewie, blood sprays from the pursuer's wound. However, the blood stains from the wounds immediately vanish one second after hitting the floor.
The type of gun Riccardo is using is a flintlock pistol which can only fire a single shot and takes a long time to reload. However, Riccardo is never shown or heard reloading it between shots.
When being chased by Riccardo, Fiona can order Hewie to pounce on Riccardo and injure him; this renders Riccardo unable to move for a few seconds allowing Fiona to take various items off Riccardo. However, during that entire time Riccardo is on the ground, Fiona cannot take Riccardo's gun away from him.