No one who goes out in the rain is ever not wet when he or she comes back inside.
On the roof in the rain they fall off into a tub of water but when they go into Ollie's house they're dry.
The leis worn by Stan and Ollie change color (yes, it is a black and white film, but check the contrast between the light and dark shades). Also, in the attic scene, Stan wears two and Ollie one; yet in the scene before, they both had two. The fezzes also seem to have magic dents.
At the beginning of the film, when Stan and Ollie return home from their lodge meeting and there's confusion over which house Stan is in, the light in Stan's house (visible through the glass panel in the door) keeps changing from off to on and back again.
Ollie says that they ship-hiked home after being shipwrecked. Stan puts his right elbow on Ollie's knee, but when the shot moves from close up to long shot, it's Stan's hand that is then on Ollie's knee.
The copyright date shown on the film reads MCMXXXIV, which translates as 1934. The film was released in December, 1933, which should read as MCMXXXIII.
In the back of the cab on the way home, every time Hardy leans in to talk to Laurel, his shadow falls across the rear-screen projection of the traffic seen through the back "window" of the cab.
When Laurel and Hardy frantically stumble about in the hallway prior to going up to the attic, the same sound effects are used over and over many times in rapid succession.
When the wives are in the cinema watching a newsreel of a car race, the cars are going left to right but the audience's heads are turning right to left. In actual fact there should be no need for the audience to turn their heads. Additionally, while Betty's head turns, her eyes remain focus on a single point before her.
In the colorized version, the newsreel is shown in color. Newsreels were exclusively in black and white at the time this film was made.
When Lottie runs into the house to answer the phone, the camera tilts up just a bit too high, revealing the beams, wires, and mechanics of the studio ceiling at the top of the frame for a brief second.
In the first wide shot in the ship docking area, before Laurel and Hardy's wives arrive, following news of the Honolulu ship sinking, a crew member and camera tripod are clearly visible reflected in a glass door.
When Ollie is being pelted by his wife with china at the end of the movie, you can see five or six studio lights clearly reflected in the enamel pot he is wearing on his head for protection.
Stan could have gone back into his house through the back entrance.
At the lodge meeting it is established that the convention in Chicago is the following week. A cruise from Los Angeles to Honolulu would take at least 6 days. So by the time they would arrive in Honolulu they would have need to depart for the return trip.
When Laurel and Hardy are returned to their wives by the police officer, as they are led inside the house, the camera tilts back slightly and the boom mic is visible at the top of the frame as they walk toward the couch.