Revealing mistake: In "Stop That World, Series 3, when Barry gets thrown of the See-Saw by the globe, and Barry lands in Paul's arms. The first shot is of a dummy and quickly switches to the second shot of Barry. It is obvious they used a dummy to make it look like Barry was falling into Paul's arm before switching them quickly.
Revealing mistake: In "Cycle Crazy, Series 3, Paul rides through the tunnel on his bike only to ride out again when a big truck comes the same way. It is obvious that the shot of Paul and the lorry are two separate shots, because after Paul comes back out, the trees don't follow the same pattern as the previous shot. This also happens between the shots where Paul rides into the tunnel.