Arbitrary Fusion (勝手にフュージョン; Katteni Fyūjon) is a type of fusion that appears in Dragon Ball Fusions. The results surpass even EX-Fusion in freedom of variety. There are over 50,000 possible combinations.
While referred to as a "fusion", Arbitrary Fusion more closely resembles the absorption ability used by Buu, as the instigator of Arbitrary Fusion will be the completely dominant fusee - retaining their name and personality once the fusion is complete, though with the addition of "KF" in front of their name.
The KF stands for Katteni Fusion, which means Arbitrary Fusion.
KF Kid Goku (Broly fused) in base-Super Saiyan 3
KF Goku (Magetta fused)
KF Goku in the merger of Goku's Super Saiyan 3 and Super Saiyan Blue forms
KF Goku (Broly fused) in Super Saiyan 3-Super Saiyan Blue
KF Goku (Vegeta fused) in Super Saiyan Blue
KF Krillin (Goku fused) in Super Saiyan Blue
KF Vegeta (Goku fused) in Super Saiyan God-Super Saiyan Blue
KF Vegeta (Goku fused) in Super Saiyan Blue
KF Vegeta (Goku fused) in Super Saiyan 4
KF Frieza (Goku fused) in Super Saiyan God
KF Frieza (Beerus fused) in Golden Frieza form
KF Broly (Vegeta fused) in Super Saiyan/Legendary Super Saiyan