Plumb Crazy - S4-E1
Continuity mistake: When the fountain's head flies off, Barry bends down and puts his hand on Paul's right shoulder. In the next shot, his hand is suddenly on Paul's left shoulder and a few seconds later in the next shot it's back on Paul's right shoulder again.
Cycle Crazy - S3-E13
Continuity mistake: When Barry takes the Guinea Pig out of his sachel, in the next shot, when Paul walks off and Barry comes into the shot, the Guinea has disappeared from his arms as he picks up his bike.
Continuity mistake: When Paul gets his hand trapped in the window and when Barry can't switch off the alarm, Paul takes his hand out that's trapped in the window and switches it off, when his arm should be stuck in the window.
Continuity mistake: In "Matchstick Men" from Series 11, Paul is pretending to be ill, and when Barry is distracting, his trousers are red, but when he enters the bedroom his trousers are yellow.
