Most likely a Waddle Dee or Waddle Doo so they don't waste the coding.
Edit:
A funny Idea I got, if we're gonna have an assist trophy from Mother, it better be Wess shaking his butt on a dance that takes about 30 seconds to finish, after that, the opponents are all stunned, receive 50% damage and KO after a while. Of course you can cancel the OP attack by just attacking him.
Just like Lucas's Project M Smash Taunt.
Would be hard to sprite, though

Since anime characters are officially done for the roster, here's a list of ideas for anime charracters as assist trophies plus just some other ideas:

Zoro - Acts similar to Renji without the final move perhaps, I wouldn't mind it though.
Crocodile - Makes sand tornadoes on stage.
Pain - Comes in and does Almighty Pull then Push to send enemies away.
Kakashi - Either does Lightning Blade or Kamui to teleport opponents off stage.
Saibamen - Runs after opponent, grabs them and explodes.
Grimmjow - Does a Cero.
Mephiles - Multiples himself and goes around the stage fighting.
Piranha Plant - Shoot fire balls.
Axl - Uses copy shot to turn into opponent and fight against him.
Shadow Link - Summons Big Bomb that damages all opponents.
Bryne - Jumps around and sends magic blast at enemies.
Viridi - Manipulates the ground to strout up plant traps.
Kefka Palazzo - Summons purple meteors to fall on stage.
Viewtiful Joe - YOU ALREADY KNOOOOOOOOOOOW!!!!

bring Jeff back

Hippie - Uses a bullhorn to imitate the fighters' mothers calling them. 50/50 chance of resulting in one of two outcomes: either everyone's attack increases (cause they didn't fall for it and are pissed as a result) or everyone is stunned for a short while (cause they fell for it).

What game is this hippie from and is this attack relevant to what he does in that game?

^Right, should've clarified, my bad.
He's from Mother 1, and yes that's more or less what he can do when you encounter him

It's also one of the toughest enemies in the first town and the primary reason that game needs a remake

^There's the 25th Anniversary edition patch which revamps the graphics and makes things easier, and then there's this:
https://forum.starmen.net/forum/Communi ... her-Remake

Shanks : He does Conquerors Haki, and whoever is facing his way/whoever is close to him automatically is unable to do anything for 5 seconds

CLEOD-BOT: Hijacks one player's controls (Including the person who summoned him) and does whatever he feels like (Including actually fighting, running off the cliff intentionally, holding Shield until it breaks, etc.) If a Sandbag gets hijacked, they keep control of theirselves and gain 10% attack power whilst CLEOD-BOT is in play

Hey, Cleod9 was gonna be an Assist Trophy way back when, let's pass the baton

Do you think Viewtiful Joe got scrapped or if he won't show up until the full game...
I nominate Klonoa to replace Pac-Man as an Assist Trophy.

Uh... exactly how? I think Ms. Pac-Man would be a better replacement so they don't waste the coding.

On second thought, that would be a good idea, all you gotta do is edit the sprite...
For klonoa, he could grab an opponent, jump near a ledge, double jump, and send them flying downward, then flop his ears to go over to the stage, pose, then disappear...or that'd be way too cheap.

Klonoa would be better off as a playable character.

Who thinks Viewtiful Joe will be cut from the game because we haven't seen him....