The final effect of this card does not specify that the monsters owned by your opponent have to come into your possession by this card's effect, meaning cards like "Creature Swap" or "Snatch Steal" can be used to give this card a 300 ATK boost.
This card can be easily Fusion Summoned by using "Edge Imp Frightfuloid", which treats itself as a "Frightfur" card, and monsters Special Summoned by the effect of "Designer Frightfur", which are treated as "Frightfur" monsters, as Fusion Materials. Additionally, "Fluffal Patchwork" is treated as a "Fightfur" card while it is on the field.
The effect of "Edge Imp Tomahawk" can be used to send "Frightfuloid" from your Deck to your Graveyard, and have "Tomahawk" gain the name of "Frightfuloid" and archetype condition. This will allow 2 of the requisite Fusion Materials for this card on your field and in your Graveyard, which "Frightfur Fusion" can be banished to Fusion Summon this card.
One odd way to Fusion Summon this card during your opponent's Battle Phase is by using "Magical Hats", to Special Summon 2 "Frightfur" non-Monster Cards such as "Frightfur Factory", "Frightfur Fusion" or "Designer Frightfur" from your Deck which will be treated as Normal Monsters. Immediately use "Flash Fusion" to Fusion Summon this card using the 2 "Frightfur" non-Monster Cards treated as Normal Monsters and another "Frightfur" monster under your control. "Paradox Fusion" can be used to prevent this card's destruction on your opponent's End Phase.
The effect of "Fusion Tag" can be used on one of your monsters, and have it copy the name of a "Frightfur" monster in your Extra Deck when said monster is used as a Fusion Material for this card.