After Timon and Pumbaa head for bed after Simba and Nala's argument, their bed is made of leaves. When Nala is trying to explain Simba's story, the bed is now made of straw.
The hyenas' paws constantly go from three toes to four off and on throughout the entire film.
When Timon is rewinding the movie at the end, the Disney logo at the beginning plays like it's in fast-foward, instead of rewind.
At their first home by the water hole, Pumbaa hands Timon a drink in a coconut shell with a straw and umbrella. As Pumbaa starts to leave in the next shot, the straw is gone, yet Timon seems to be holding and drinking through it. In the following shot, the straw is back.
When Timon and Pumbaa first meet up with each other and continue to scream it is daylight outside. But the previous shot was night time.
Timon and Pumbaa wake up to find the "I Just Can't Wait to Be King" sequence 1 day after they saw Rafiki holding Simba having just been born at Pride Rock, which surely would've actually taken place weeks after then.
When Rafiki is hanging upside down, the white fur/mane around his neck does not hang down as it should. Instead it just remains in place like there was no gravity.
In the 'Can You Feel The Love Tonight' sequence [in the French track], after Timon and Pumbaa have catapulted into a tree, in the song you can hear a gasping noise. The song was taken from the first Lion King and the noise was Nala gasping for breath after Simba pulled her into the water.
In the film, Pride Rock is shown as being very close to where the "I Just Can't Wait to Be King" sequence takes place. In the first film, this is not the case as Pride Rock is nowhere in sight.
During the entire film, Rafiki appears to be Timon's mentor, yet in the first Lion King film---when Rafiki says what happened to Simba--Timon asks, "Who's the monkey?"
In the first Lion King movie, near the end, Scar blames everything on the hyenas and that is why they turn on him (at the end, after Simba throws him off the ledge). In this movie, it shows the hyenas being lured away from the final conflict between Scar and Simba, therefore they would not have heard Scar, and thus contradicts the first movie.