Continuity mistake: During the long shot when the cast are racing across Tower Bridge in the double decker bus, right in the middle of the screen you can see the twinkling lights of a distant skyscraper which looks suspiciously like Canary Wharf, which of course had not yet been built in 1935. Its construction was in fact not completed until 1990. (00:45:05)
Factual error: If rockets were to attached to the basket of a balloon, the balloon would remain in the same spot but the basket would spin around it, due to the flexible ropes between the basket and balloon. (01:19:00)
Factual error: Our Heroes are running after the Bad Guys who have kidnapped their "Precocious Kid." They are chasing them in a dirigible. We see them flying across the full Moon. A few nights later, we see them flying across... the full Moon. The phase of the Moon is probably the single most abused astronomy idea in movies (besides sounds in space). The Moon goes through phases as it orbits the Earth. The phase changes every night, and the difference over even two nights is pretty clear. It's possible, just, that over three nights the Moon can be almost full, then full, then a little past full. But usually the Moon is very different over the course of that much time. Really, the phase should have changed quite a bit during the chase. (01:00:25 - 01:22:50)
Revealing mistake: At the beginning of the movie we see Rick and Evy almost drowning in crystal clear water. Had that water really been from the Nile, it would have been muddier.
Revealing mistake: During the final battle, when the burning oil-pots are being knocked over, you can see the weapons on the sides are rubber from the way they bend and wobble.
Revealing mistake: In the opening battle, when the armies organize before charging, you can see some men walking right through each other, where digital doubles have been added into the scenes. Hard to catch, but it happens at least once or twice.
Continuity mistake: Towards the end, where the pyramid is sucking up the oasis, and everyone is jumping on the dirigible, Jonathan's slash on his chest from fighting Anck-Su-Namun has mysteriously healed, and there is no blood, although his shirt is still cut. (01:47:15 - 01:58:55)
Continuity mistake: When we first enter the museum there is a long shot of the resurrection area with Evie at the top of the screen lying on a wooden stretcher. She is conscious and seen moving around to adjust the ropes. In the next shot, she is unconscious and is only woken once she is bumped on the table. (00:35:35)
Deliberate mistake: At the beginning, we see the Scorpion King leading his army into battle. However, despite people being stabbed with swords, and slashed, there is no blood on any of the soldiers, nor on their weapons. Kind of hard to believe war was that clean back then. (00:01:40)
Deliberate mistake: According to the DVD version, the Army of Anubis roars in ARABIC. Rather strange for a monstrous army of an ancient Egyptian god... (01:44:15)
Continuity mistake: When the family is on top of the pyramid, in one shot Brendan Fraser has stubble, then in the next shot he is completely clean shaven.
Revealing mistake: In the battle against the Anubis Warriors, you can see the CGI sand explodes "wrong" sometimes. In other words, the sand sometimes overlaps the wrong areas, such as people that are in front of it.
Revealing mistake: During the fight against the Anubis warriors, in one shot you can see two men stab one of them in the chest. The warrior explodes and when the sand clears only one man remains. This is because all of the men were photographed separately and digitally composited together, so one of the computer artists made a mistake and accidentally cut out a character half-way through the shot.
Revealing mistake: When the Nile explodes through the corridor in the beginning, as the villain's goon is running by, you can see the wall suddenly get a little bit lighter in a circular fade pattern. This reveals that two separate images were used, and they were composited together. One day the goon was filmed, then another, the water bursting through was filmed, and the lighting was slightly off.
Continuity mistake: As Imhotep hangs from the ledge his arms change position several times.
Deliberate mistake: When Rick and Imhotep battle man-to-man at the end, in one shot above them you see steam blasting from the side of the screen. Problem is that when the angle changes, it's clear that area is just empty space, so the steam came from nowhere. (The DVD commentary mentions that they always had people with flame-throwers and steam-machines right off-screen to blast fire and smoke to make certain scenes more dramatic).
Continuity mistake: When you first see Oded Fehr's bird of prey (At Izzy's Place), it flies towards him, but it appears there's a line tied to the birds' leg that is either translucent or has been digitally covered over. (00:56:05)
Factual error: When the dirigible is passing Abu Simbel (where the four sitting statues are), the second one from the left is broken, which is accurate. However, in reality, the rubble is sitting at the foot of that statue, not a considerable distance in front of it like it was as they passed.
Audio problem: When the first fight happens at the house, we hear Alex tell his mom to look out, but he's actually not saying anything, he's just standing there quiet.
Revealing mistake: During the very first shot of the scene where the heroes arrive in the canyon (during the "Wall of Water" scene), pay attention to the shot carefully as the camera tilts down, as several elements seem out-of-place. When Imhotep steps into frame, the lighting on him doesn't quite match the scenery around him (indicating he was shot against a blue or green screen and added into the shot), and the waterfall in the background moves somewhat unnaturally (slightly jittery if you look closely) towards the end of the shot.
Answer: He says that it means 'it's as hot as hell'.