Dragon Ball Z Movie 12: Fukkatsu no Fusion!! Gokuu to Vegeta aka. Fusion Reborn is a movie where the death return to life after an accident happened in hell creating a monster known as Janemba. It is up to Goku, Vegeta and Paikuhan (or Pikkon in American) to stop Janemba from destroying the balance of the circle of life pretty much.

The movie does a good job in showing the chaos Janemba's existence has to both the afterlife and the living world as the viewers will be able to see both what is going on in these different locations.
While Goku, Paikuhan and Vegeta deal with Janemba while Gohan, Goten, Trunks and Videl do their best to deal with the revived villains amounts which is Frieza. The movie also uses two artstyles for the serious and non serious moments but not necessary for comedic scenes. There are references to famous movies or historical events that get parodied which some countries won't be able to see because of censorships like the infamous dictator scene being removed from the German dub.
Speaking of artstyle, the visuals and animations are even holding up today and are the best looking Dragon Ball visuals up to date. Animators took full advantage of the tools they had making Janemba's abilities especially the teleportation a visual spectacle. It is alongside Wrath the Dragon and Path to Power without the doubt the best looking Dragon Ball film.
There is a good reason why this alongside Wrath of the Dragon are the only Dragon Ball movies from the original run that had a worldwide theatrical release.

As the name of the movie suggests, the selling point is Goku and Vegeta fusing to Gogeta being the first time these two merge to stop a common enemy. And the build up to that moment was done beautifully.
We see more about Vegeta's inferiority complex and the hate of the idea to fuse with his rival. And it might even rival Vegeta's development throughout the Boo Saga.
While on the topic of Boo Saga, this movie can't fit to the main story timeline and can be seen as a sidestory where the good guys defeated Boo with Goku and Vegeta remaining death.

Janemba is a villain that resembles Boo a lot but is created out of pure evil. He starts off as a fatso and later becomes a muscular demonic lizard thingy after one of the creepiest transformation scenes ever. His abilities are also very unique to him but it feels like there are also too much powers of Boo added for no reason like arm extension. But the main appeal obviously is altering objects and teleportation. Not only can he teleport himself but can also create teleportation portals which he cleverly uses to attack opponents without physically appearing or sending back attacks aimed at him. Meaning he can use his abilities as offensive and defensive tools.
But personality wise he is inferior to Kid Boo after he turned evil. Since he can't speak, most of his emotions are expressed by emoting with his body. He is also the only character in the series that uses a physical weapon after the Frieza Saga and makes it being dangerous believable as something like a Sword for Future Trunks didn't enhance his fighting abilities and was just visually pleasing.

Comedy in this movie is also great as jokes some which had build up in this movie or from the show being viewed. It would be hard to explain some of them without spoiling it. But they aren't the only ones.

The environment is another thing notable for the movie as viewers of the anime have had seen hell, but now that Janemba appeared viewers can witness how Janemba's existence altered it. Combining the flying multi-colored giant jelly beans created by Janemba and the unusual color scheme of hell creates one of the most surreal landscapes in the franchise. Simply put, changing an already explored location into a brand knew one.

Like always there are some criticism. Of all the villains from the show that returned, only one fights and gets defeated in an underwhelming way. I think you can guess who is it. Someone who just won't stop returning. Pretty much wasting the potential of old villains getting a second chance to get what they want and taking advantage of the secondary cast better like Piccolo, Yamcha, Tien, Chaotzu and Krilllin to beat someone like Bojack, Turles or Lord Slug. Instead most of the living world scenes are wasted for historical jokes and Goten and Trunks.
As with most DBZ movie villains who are similar to the current story arc villain that came out around the time, Janemba is basically similar to Boo. While he has some unique abilities and a killer design, he just feels like a watered down version of the last DBZ villain. Both start out fat and at the runtime of the Boo Saga the latest form when this movie came out was Super Boo and Janemba's final form has a similar body structure. And as a character, he is shallow after his transformation who had a childlike innocent personality. And there is the question why he is as strong as he is. Another problem is the transformation from big to small is that in regards to Boo who is made out of magic and bubble gum substance, Janemba's transformation that happens in a similar matter seems unrealistic because it doesn't have a believable excuse like Boo. It also makes it less believable that Janemba can extend his arms, an ability it didn't even need. One other issue is neglect of Paikuhan as a character. While he did appear to help out, most of the time he was just trying to free Enma or King Yama, only appearing to buy time for the fusion briefly. So he was wasted as a character for most of the film.

Overall Fusion Reborn is a good movie still well remembered and the movie that made Gogeta the character everyone loves. This movie has the debut of Super Saiyan 3 and might be the best use of the transformation in the franchise. Even the transformation scene of Super Saiyan 3 surpasses the one in the Boo Saga version from the anime version taking advantage of how the environment shifts as well as the tone from the battle from fun to serious. So if you like more development for Vegeta, love fusion especially Gogeta and wants some good Super Saiyan 3 action, you owe yourself to watch Fusion Reborn.