Just noting how funny it was that a lot of these didn't come true in any form, and others (like Wolf and Olimar) ended up being playable
A few more assists because I'm lamenting the short supply:
Cranky Kong -- Shuffles back and forth on his cane, complaining about the characters in similar fashion to Mr. Resetti. If a character idles near him he can grab them and smack them lightly with his cane for 1% damage a hit, but he's mostly an annoyance since he's in the background of the stage with Pokemon Trainer. On Jungle Japes, it's Wrinkly who offers encouragement and does no damage before flying away.
Captain Syrup -- Gives a hearty laugh, then leaps into the air after rubbing and throwing down a lamp. She reappears on the shoulder of a genie who begins to throw lightning bolts down at the stage. The lamp can be grabbed, hit, and tossed around as an item. Each time it lands, it spews out a cloud platform that rises. The genie is a powerful assist and when he's finished Syrup leaps back onto the stage and both disappear along with the lamp.
Duck Hunt Dog -- Bushes appear along the background of the stage and the hound begins to sniff around before barking and hopping into the bushes. Ducks fly across the screen and can be targeted by players, giving them "points." If all the ducks aren't KO'd, the dog appears to laugh at the players before disappearing. More of a "fun" assist than anything. The ducks appear in a massive flock sometimes, like "bullet hell" in a shmup game.
Takamaru -- As an assist, Takamaru disappears in a flash of smoke and begins tossing kunai at random players from his standing position. He then runs about the stage, only his shadow visible, and slashes if a player gets near him. He deflects projectiles that connect with his body as well. Before disappearing, he becomes visible again and taunts.
Sukapon -- As an assist, Sukapon dances. After a few seconds of this, he then rears back and does the Skapon Roll forwards. If he hits a player he rebounds and loses his head. He screws it back on before disappearing.
Fox -- A different fox, this time the one from Eggsplode. Nests appear around the stage and the fox sneaks in the background placing bombs under random ones. Eggs in the nests can be cracked for items, but if you grab one with a bomb inside...
Tropical Fish -- A Game and Watch assist? o.O A 2-bit fish moves across the stage in a very uniform fashion (leaving the LCD afterimages in its path as well as before it). If a player grabs the fish before it touches the ground, they receive a bonus item. If a fish touches the ground, a cat appears to eat it and the players get nothing.
Balloon Man -- Another G&W assist, Balloon Man appears also in LCD form. He flies to a corner of the screen with his jetpack and fires bullets at the stage. They come slowly, but they pack a punch.
Fiery Blowhog-- A Pikmin assist, the Fiery Blowhog wanders the stage happily. It will stop from time to time to blow a massive wave of fire, burning players. If attacked or jumped on, it will shake violently and spin around, blowing a mighty gust of wind that pushes players backwards.
Marvellous Boys -- I forget their name, but the three of them appear on piggyback. They rush towards a player as "one tall character" and tackle them. When they do, they tumble and roll onto the ground laughing before disappearing. They are hard to jump over.
Donbe and Hikari -- Donbe appears and bounces back and forth while Hikari yells to him from the background. He leaps to a position on the stage and continually tosses spears similar to Arthur from Ghost and Goblins.
Gokuu -- Flies around on a flying nimbus and launches small bolts at players as he buzzes around the stage. You can kick him off the cloud and ride it yourself, but the path is erratic. Sometimes Gokuu is "killed," but most of the time he will recover on the ground and slap players with his extending bo staff.
Time Twist Kid -- He doesn't do too much. When he appears, he breaks the flow of time and speeds up the battle before disappearing.
Mike Jones -- As an assist, Mike uses his patented "Time Slash" ability. He winks at the screen, then leaps towards a player and whips them with his yo-yo. If he connects, he begins a volley of strikes using all sorts of history-inspired weapons: stone axe, katana, Excalibur, baseball bat, laser pistol, morning star, etc. This is done in a "one frame each" fashion, so they attack appears to be moving ultra-fast. When finished, he lands a mighty kick from his cleets and sends the player flying.
Zoda -- Star Tropics Zoda. He appears in his caped form from Star Tropics II. Zoda hovers above the stage tossing energy balls that explode on contact with the floor but pass through players. If struck while hovering, his cape and helmet fall off and disappear revealing the fetus-like alien underneath. His attack pattern does not change, but he can take damage and be "forced" to leave.
Mica -- Appears and disappears in a flash of light. A rain of shooting stars fall to strike the stage, weaker than PK Starstorm but significant enough to deal damage. When she appears she says a Star Tropics inspired line: "Anything is possible under the Southern Cross."
Ayumi -- Looks around worriedly and drops her briefcase. She bends to pick it up when a ghost appears behind her and spooks her, causing her to run around crying. She knocks players out of her way as she does this. Her briefcase becomes a weapon you can grab, and if players are near her when the ghost pops they too can be "shocked" by its appearance.
Wanda -- Flies around the stage tapping players on the shoulder, turning them around. A nuisance more than anything. She can be attacked.
Kamek -- Flies out on his broom, but jumps off to cast a spell. Yells "Hocus Pocus!" like Tetris Attack and fires off his patented magic spell. It damages players, but the more important thing is that it will turn beloved item containers into Subspace enemies. Kamek will teleport about the stage to avoid contact. If a spell hits an already summoned enemy, said enemy becomes "Giant."
Demon -- From Power Soukoban, this little demon wanders the stage. She can push items like Mr. Saturn and tries to "escape" the level more or less. As she's about to disappear, she does her "victory dance" and steps off the level. She cannot be attacked, but she does sometimes blow fireballs that will "wisp" around the stage and hit random targets (usually item containers).
Raiden -- He appears all tough like, then winces when he sees the fight. Raiden crawls in the background of the stage to avoid detection, then leaps from the edge when he reaches it. He's pretty useless.
btw, item idea I really liked: Magazine, from MGS2 -- toss this on the ground. it will distract players who step over it and cause them to pause for a second.
Nack the Weasel -- Another Sonic summon, and one of my faves. Nack fires a few shots from his popgun, then bounces on his crooked tail off the stage.
Flicky -- Another Sonic summon, though more based in classic SEGA. Flicky is followed by a line of yellow chicks. He kicks items at players to deal damage, but if he himself is hit the chicks will separate and flee. Flicky runs desperately to recover them and moves a lot faster in the process. He doesn't always get all the chicks before disappearing.
