Continuity mistake: At all times, the enchanted rose is on a smooth marble table, except for when the Beast roars with pain after Gaston shoots him with an arrow. In this shot the table is wooden.
Continuity mistake: Just after the Beast tears the painting, look carefully out the window and you'll see a carving of a person with his mouth open on the balcony. Then when the shot zooms out of the castle, this carving is gone.
Continuity mistake: At the start of the song "Kill the Beast", the mirror keeps coming closer and further away from the buckle on Gaston's belt.
Continuity mistake: Belle takes a blue book from the library, but in the shot where Gaston sings "I'm making plans to woo and marry Belle" the book is now brown.
Continuity mistake: When Belle is reading her book inside, there is a black teapot over a plate on one of the shelves. Moments later, the plate is to the teapot's side.
Continuity mistake: When Maurice enters the castle, the front doors have four planks each. For the rest of the film, they have five planks each.
Continuity mistake: The width of the grey rings on Maurice's lantern changes in the scene where he is lost in the forest with Phillipe.
Continuity mistake: When Belle is reading her book by the table, a shelf over the fireplace is visible below another shelf to the left of it. Moments later, after Gaston has entered and Belle asks "What do you know about my dreams?" this shelf is above the shelf to the left of it.
Continuity mistake: After Belle sees the painting in the West Wing, there is a shot of the table where the enchanted rose is. In this shot, the magic mirror is not on the table. In the next shot, it is. Then when the Beast yells "Get out." it is gone again.
Continuity mistake: When Belle finds Maurice locked in the dungeons, the bars change from black to brown in different shots.
Continuity mistake: When Belle comes to the West Wing, she approaches a cracked up mirror. Then in the shot where she is shown right in front of the mirror, the crack on the top right is much wider, and many cracks are differed etc.
Continuity mistake: When Mrs. Potts and Chip first come into Belle's room at the castle, Chip spills tea onto the carpet. In the next shot, the tea is gone.
Continuity mistake: At the start, the Beast tears a painting and makes ten equal sized gashes. Later, Belle is exploring and sees this painting; there are now nine little gashes and one huge gash.
Continuity mistake: When Belle enters the bookstore, the windowsill is red. When she comes out of it, it is white.
Continuity mistake: Gaston's socks are red when he is in the mud. When he walks away, we briefly see them as being orange.
Continuity mistake: When Maurice arrives at the castle and loses his hat, the bricks the hat is over change between shots.
Continuity mistake: When Belle is walking home with her book and goes up a wheelbarrow, the sacks of flour on the wheelbarrow move closer together between shots.
Continuity mistake: During the song "Gaston", Lefou throws a lot of eggs in the air, but very few come back down.
Other mistake: At no point in this movie is the background of a room ever reflected in a mirror - even if the characters themselves are reflected in it.
Continuity mistake: When Gaston and Lefou are talking to the man in the bar, Gaston throws the bag of gold to the lantern's right. However, when this man says, "So you want me to throw her father into the asylum?", the bag is now on the lantern's left.
Answer: In the prologue, it states that the Beast must find true love by his 21st birthday, and that he had been cursed for ten years, so since his relationship with Belle takes place as the deadline approaches, he must have been 10 when he was cursed.