Many times throughout the Z/GT series, the Z-Senshi use the versatile technique of “Fusion”. This means

Part 1

Types of Fusion: (There are five methods of Fusing used in Z/GT.)

Ø    Metamorian – Son Goku was taught this type of Fusion while he was training in the Afterworld, by the people of Metamori. The two warriors must perform a complicated and synchronized dance, resulting in a warrior with both the physical/mental traits of both warriors. These fusions last 30 minutes unless otherwise stated. 

Ø       Potarra – This type of Fusion involves the use of the Kaious’ earrings. One warrior puts a single earring on his left ear, while the other warrior puts the remaining earring on his right ear. There is a head persona (meaning one of the warrior’s personalities takes slighter more control over the newly produced warrior’s mental facade). Permanent until broken chemically.

Ø     Absorption (a.) – This method of absorption is used by Majin Buu. He takes advantage of his goo-like body and literally absorbs someone else within it. (b.) This method was used by Cell, via the “stinger”-like absorber on his back. (c.) In this method one digests another to fuse with them. All are Permanent until broken manually.

Ø     Namekian – This Fusion technique is actually more like the Absorption method than any other. One primary Namekian being voluntarily “absorbs” the soul/spirit/chi of the other warrior. The primary being looks/acts the same, except with the knowledge and power of the other one. Permanent.

Ø     Miscellaneous – another “Fusion” is performed in the series. It is given no name, but is technically a Fusion in theory. The two warriors charge their chi, and then channel both their energies together, resulting in a new warrior. Permanent.

Part 2

Fusion #0a
Warriors: Elder Kaioshin, a witch
New Warrior: Elder Kaioshin (ugly)
Fusion Type: Potarra
Need for Fusion: Accidental.
Result: Elder Kai gained some power raising abilities

Fusion #0b
Warriors: Kid Buu, South Kaioshin
New Warrior: A muscular Buu form
Fusion Type: Absorption a.
Need for Fusion: No need.
Result: Became stronger, yet not as strong as Dai Kaioshin

Fusion #0c
Warriors: Muscular Buu, Dai Kaioshin
New Warrior: Fat Buu
Fusion Type: Absorption a.
Need for Fusion: No need.
Result: Buu became more controllable by Bibidi...yet with a good side.

Fusion #1
Warriors: Piccolo, Nail
New Warrior: Piccolo
Fusion Type: Namekian
Need for Fusion: To avenge the Nameks and defeat Freeza
Result: Lost when Freeza advanced to Form 3

Fusion #2
Warriors: Piccolo, Kami
New Warrior: Piccolo
Fusion Type:  Namekian
Need for Fusion: To defeat the androids and a new threat, Cell.
Result: Battled Cell and 17 to draws, then nearly got killed by Cell.

Fusion #3
Warriors: Cell, 17
New Warrior: Cell Stage 2
Fusion Type: Absorption b.
Need for Fusion: To get closer to Perfection
Result: Was almost killed by Vegeta and Trunks.

Fusion #4
Warriors: Cell, 18
New Warrior: Perfect Cell
Fusion Type: Absorption b.
Need for Fusion: To reach Perfection.
Result: Defeated everyone and put the Earth into jeopardy.

Fusion #5
Warriors: Goten, Trunks
New Warrior: Fat Gotenks
Fusion Type: Metamorian
Need for Fusion: To defeat Fat Buu
Result: Couldn't even run.

Fusion #6
Warriors: Goten, Trunks
New Warrior: Skinny Gotenks
Fusion Type: Metamorian
Need for Fusion: To defeat Fat Buu.
Result: Could hardly walk.

Fusion #7
Warriors: Goten, Trunks
New Warrior: Gotenks
Fusion Type: Metamorian
Need for Fusion: To defeat Fat Buu
Result: Lost badly to Fat Buu

Fusion #8
Warriors: SSJ Goten, SSJ Trunks
New Warrior: SSJ Gotenks
Fusion Type: Metamorian
Need for Fusion: To defeat Fat Buu.
Result: Wasted time showing off, and unfused as he was challenging Buu.

Fusion #9
Warriors: Fat Buu, Thin Buu
New Warrior: Super Buu
Fusion Type: Absorption c.
Need for Fusion: Simply to gain strength
Result: Killed off almost the whole Earth population.

Fusion #10
Warriors: Goten, Trunks
New Warrior: Gotenks
Fusion Type: Metamorian
Need for Fusion: To defeat Super Buu.
Result: Soon went SSJ, but was still being beaten badly.

Fusion #11
Warriors: SSJ Goten, SSJ Trunks
New Warrior: SSJ3 Gotenks
Fusion Type: Metamorian (20 min)
Need for Fusion: To escape dimensions and kill Super Buu.
Result: Escaped dimensions and was about to finish Super Buu when the fusion wore off.

Fusion #12
Warriors: Goten, Trunks
New Warrior: SSJ3 Gotenks
Fusion Type: Metamorian (20 min)
Need for Fusion: To fight Super Buu, who wouldn't fight Gohan
Result: Was absorbed.

Fusion #13
Warriors: Buu, Gotenks, Piccolo
New Warrior: Gotenks Buu
Fusion Type: Absorption a.
Need for Fusion: To defeat Gohan.
Result: Almost killed Gohan, but when Gotenks unfused, was almost killed.

Fusion #14
Warriors: East Kaioshin, Kibito
New Warrior: Kibito Kaioshin
Fusion Type: Potarra
Need for Fusion: To test the Potarra method
Result: .....nothing really.

Fusion #15
Warriors: Buu, Gohan
New Warrior: Gohan Buu
Fusion Type: Absorption a.
Need for Fusion: To avoid being killed by Gohan.
Result: Caused Goku to panic.

Fusion #16
Warriors: Goku, Vegeta
New Warrior: Vegitto
Fusion Type: Potarra
Need for Fusion: To defeat Gohan Buu
Result: Dominated Gohan Buu, but eventually was absorbed (unsuccessfully).

Fusion #17
Warriors: Goten, Trunks
New Warrior: Gotenks
Fusion Type: Metamorian
Need for Fusion: As a joke, to fight Goku in the bath.
Result: Chi Chi got pissed.

Fusion #18
Warriors: Goku, Vegeta
New Warrior: Fat Gogeta
Fusion Type: Metamorian
Need for Fusion: To defeat Janemba.
Result: Got beaten up badly.

Fusion #19
Warriors: Goku, Vegeta
New Warrior: SSJ2 Gogeta
Fusion Type: Metamorian
Need for Fusion: To defeat Janemba
Result: Won the fight.

Fusion #20
Warriors: SSJ Goten, SSJ Trunks
New Warrior: Gotenks
Fusion Type: Metamorian
Need for Fusion: To defeat the German WWII army.
Result: Destroyed it, leaving a very unhappy Hitler.

Fusion #21
Warriors: SSJ Goten, SSJ Trunks
New Warrior: SSJ3 Gotenks
Fusion Type: Metamorian
Need for Fusion: To defeat Hildegarn
Result: Caused Hildegarn to shed into a second form.

Fusion #22
Warriors: Uub, Fat Buu
New Warrior: Ubuu
Fusion Type: Miscellaneous
Need for Fusion: To defeat BebiVegeta
Result: Got eaten by Bebi

Fusion #23
Warriors: 17, Hell 17
New Warrior: Super 17
Fusion Type: Miscellaneous
Need for Fusion: To become the ultimate fighting android.
Result: Beat everyone, except later was killed by the team of Goku and 18

Fusion #24
Warriors: Li Shenlong, the other 6 dragonballs
New Warrior: Li Shenlong
Fusion Type: Absorption c.
Need for Fusion: To have an advantage over SSJ4 Goku.
Result: Overpowered the fight, until...

Fusion #25
Warriors: SSJ4 Goku, SSJ4 Vegeta
New Warrior: SSJ4 Gogeta
Fusion Type: Metamorian (10 min)
Need for Fusion: To defeat Li Shenlong
Result: Dominates Li Shenlong but runs out of time

NOTES:

• Buu absorbed Vegitto, however this was unsuccessful, and does not count.
• Occasionally in GT, Buu lets people hide in his brain by eating them. This is not really fusion though, Buu does not recieve powers.
• Fusions 0a-0c occurred before DBZGT.
• Al fusions aside from Metamorian are dominant, meaning one side has more say.
• Goku also swallows the 4 star dragonball, however this is not a fusion because he does not gain anything.