F.F. was obtainable for a limited time as a collaboration character in the mobile game Puzzle & Dragons.
F・F
Attributes: 
Rarity: 5★ (Base)
No. 9593
HP
2,499 (Lvl.99)
ATK
3,167 (Lvl.99)
RCV
59 (Lvl.99)
Active Skill: "Foo Fighters" (Localized Name: "F.F.")
1.5x Orb move time & recovers 20% HP for 4 turns; removes Orb locks
Leader Skill: "F.F. Shot"
20x ATK, reduces damage & adds 3 combos when Wood & Water attack at once; 3x HP for Attacker Type
フー・ファイターズ
Attributes:
Rarity: 6★ (Assist Evolution)
No. 9594
HP
2,499 (Lvl.99)
ATK
3,167 (Lvl.99)
RCV
59 (Lvl.99)
Active Skill: "Intellect"
2x Orb move time for 5 turns; vastly reduces damage for 1 turn
Leader Skill: "N/A"
N/A