Continuity mistake: In the beginning when the chairman says "I suppose we could just fire him.", he lifts his hands while folding them. When it cuts his hands are back on the table. (00:01:05)
Continuity mistake: When Bean falls sleeping out of the chair, you see his left hand between his legs. In the next shot, his hand is in front of him. (00:03:35)
Continuity mistake: When David tells his wife that Mr. Bean will stay at their house, she puts her knife on the table. In the next shot when she gets up, the knife is gone. (00:07:35)
Continuity mistake: When David tells Kevin and Jennifer about Bean staying at their house and he says "Let's say there is a chart of the most intelligent people...", you can see a blue pillow on the couch which Kevin and Jennifer are sitting on. When it cuts to a shot behind them you can see the pillow is on Kevin's lap. When it cuts again the pillow's back on the couch. (00:08:15)
Continuity mistake: After Bean and David's first ride with the "Ride of Doom" when Bean asks David to get new tickets, you can see David holding a big red bulldog teddy bear. When it cuts the bulldog is suddenly gone. (00:28:50)
Continuity mistake: When David and the inspector are watching Bean in the interrogation room, you see David stand right beside the inspector. In the next shot he is standing further away, and then he is right beside him again. (00:31:10)
Continuity mistake: When Bean is in the interrogation room, the scene switches several times from Bean's view to the cop's view. In one shot, the small end of Bean's tie is hidden behind the wide end. In the next shot, the small end is visible. This happens two more times. (00:31:10)
Visible crew/equipment: When Bean is looking at the painting for the first time, he puts his hands on his hips. When he does, it lifts his jacket. When this happens you can see his mic pack clear as day. (00:39:50)
Continuity mistake: When Bean is alone in the room with the original painting when they get it, he's blowing at the right side of the frame in one shot, but blowing in the middle in the next shot. (00:40:15)
Other mistake: When Mr Bean has messed the painting up, he takes it to a room to get the pen ink off, this room is labeled "employees washroom" and inside its a workshop. (00:42:25)
Continuity mistake: The massive smear that Bean creates on the picture is different depending on the shot. This is when it first happens. (00:44:00)
Continuity mistake: When we are shown CCTV footage of Bean putting the painting back, it is the same clip as when he took the painting down. (00:55:40)
Continuity mistake: When Jennifer is going off on a motorcycle with that guy, you see Bean waving standing up straight in a wide shot, but a closer shot of him he's leaning to the left. (00:56:50)
Other mistake: When Bean was shaking the unconscious daughter in the hospital bed trying to revive her, the daughter licks her lips to moisten them right before Bean climbs on the bed. (01:15:50)
Visible crew/equipment: When Mr. Bean is in the boardroom of people discussing his fate at the beginning of the movie, there's one shot where you can see a cameraman's feet and a moving cable reflected in a shiny surface.
Visible crew/equipment: When Mr. Bean is in the operating room, there is a man standing behind a machine who is not dressed like the other surgeons.
Factual error: The establishing shot of the film shows an art gallery with the subtitle 'The Royal National Gallery, London'. Not only is there no such museum (its closest match being simply the 'National Gallery'), but the shot actually shows the Tate Britain, complete with visible red banner outside saying 'Tate Gallery'.
Answer: In the context of the movie, the "damage" has already been done, so-to-speak... he's already in the shower with Bean. And since he's also in a big rush to get to the museum, he decides to just keep showering. (In a meta, behind-the-scenes sense, it's also just funnier for him to stay in the shower rather than get out and wait for Bean.)
TedStixon