Assist Trophies work very similarly to Poké Balls. However, no Pokémon come out of them, and once an Assist Trophy is grabbed, it is automatically activated, assuming the holder is standing on the ground, and not in a jump, attack, or hitstun. Some Assist Trophies must be unlocked in order to be used, such as Gray Fox from Metal Gear. Unlike the Poké Ball, this item can be eaten by moves such as Kirby and King Dedede's Inhale, and Munchlax. In Smash 4 and Ultimate, all of the assist trophies in the base game are available from the start.
The majority of Assist Trophies in Brawl are undamageable, with only Starfy and Lakitu being able to be interrupted or otherwise hit or even KO'd. In Super Smash Bros. 4, however, some Assist Trophies can be attacked, potentially interrupting their attacks or otherwise manipulating how they perform and even being able to KO them (this can be seen by their ending animations coming earlier than normal, them having their own death animation, or simply teleporting away). However, there is no reward for KOing an Assist Trophy. In Super Smash Bros. Ultimate, more than one Assist Trophy can be on the stage at once. A larger number of Assist Trophies are also made able to be KO'd, which grants the player who KO'd them one point. When the Assist Trophy is close to becoming KO'd, the player who summoned it can KO it to prevent other players from gaining a point.
List of Assist Trophies
In Super Smash Bros. Brawl
There are 27 Assist Trophies in Super Smash Bros Brawl.
In Super Smash Bros. 4
Assist Trophies return in Super Smash Bros. 4 with a more iridescent design and a softer "popping" sound upon use, instead of the glass-shattering sound effect it had in Brawl. Unlike in Brawl, where all Assist Trophies apart from Starfy and Lakitu could not be damaged nor defeated, several Assist Trophies can now be KO'd, including several returning ones who could not be attacked in Brawl. There are 39 Assist Trophies in total, with 21 new ones and 18 returning from Brawl, while nine were cut. Both the 3DS and Wii U versions include exactly the same Assist Trophies, and unlike in Brawl, there are no unlockable Assist Trophies.
For the first time in the series, multiple Assist Trophies can appear at once. Players are rewarded points in Time battles when KOing a defeatable Assist Trophy. Occasionally, opposing Assist Trophies may fight each other. They can also now be affected by status effects such as freezing. Assist Trophies also respawn if they fall off the stage accidentally. The item itself reuses the rainbow dome from SSB4. There are 59 total Assist Trophies, with 27 new ones, 30 returning from SSB4, and two returning from Brawl after being cut from SSB4. Nine Assist Trophies from SSB4 were also cut.
On some stages, certain Assist Trophies are unable to spawn for various reasons (such as gimmicks affecting the Assist Trophy's visibility or abilities, already appearing as a background character, or even Alucard not appearing in front of mirrors).
Super Smash Bros. Brawl
A capsule that contains characters who will help you out in battle. You won't know who's in the capsule until you open it. It may be someone everyone knows or someone who's a bit of a mystery. The majority of these characters are invulnerable, so attacking them is not an option. You know what that means, right? RUN!
Super Smash Bros. 4