Before I get started, all these characters are 100 percent real, and are planned for Smash Brothers DLC. Don't ask me how I know this, I just do. All attacks for these characters are surprisingly taken from games these characters were in. If you have any suggestions for characters that "Sakurai" should add as DLC, please say their name in the comments section.
The Goomba is a lightweight character from the Mario Universe. Its standard moves consist of headbutts, kicks, and dashing at its opponents. For its up special, it grows wings, and flies. For its side special, it flips upside down, and spins towards its opponent. As its down special, it becomes squished, where it can only run around, and use its up special to come out of this state, or run into enemies to deal a small amount of damage and moderate knockback (This will also happen if it's jumped on). As its neutral special, it will attack using a baseball bat.
Other attributes of the Goomba are that they'll take more than average damage when attacked from above, but less when attacked from the sides or below. It also has a moderate speed, but doesn't jump very high. As its final smash, it will grow to about the size of Giga Bowser, greatly increasing its weight, attack power, and making it difficult to hit its head.
As for its taunts, for its up taunt, it will put on Mario, Luigi, or Wario's hat. As its down taunt, it will start bouncing rapidly, and for its side taunt, it will put on a life preserver (which it also wears in its swimming animation).
Luvdisc is a lightweight character from the Pokémon Universe. Its standard moves consist of Tackle, Flail, and Bounce. For its up special, Luvdisc will use Waterfall. For its side special, Luvdisc will use Aqua Jet. For its down special, Luvdisc will use Water Pulse. For its neutral special, Luvdisc will use Aqua Ring, which will heal a little bit of damage.
Luvdisc moves around by swimming in the air with a moderate speed. As its final smash, it uses Hydro Pump.
As for its taunts, it uses Lucky Chant as its up taunt. It uses Sweet Kiss as its side taunt. It uses Double Team as its down taunt.
Steve is a middleweight character from the Minecraft Universe. His standard moves consist of punches, and swings of his sword. For his up special, he places a ladder, climbs up it, then the ladder breaks. For his side special, he uses a Pickaxe. For his down special, he places a dirt block. His down smash can only be used 5 times unless a dirt block is broken. For his neutral smash, he pulls out a bow, and shoots an arrow.
Steve moves around at a somewhat quick speed. As his final smash, he puts on diamond armor, which increases his weight by a lot, and decreases the damage he takes from attacks.
As for his taunts, he'll throw a stack of diamonds in the air, then pick them all up for his up taunt. For his down taunt, he'll break the ground below him, then replace the broken section, unless he breaks one of his dirt blocks. For his side taunt, he will quickly build a small house, then burn it down.
Isaac is a middleweight character from the Golden Sun Universe.His standard moves consist of stabs and slashes with the Sol Blade. For his up special, Isaac will use retreat (a move that makes him teleport). As his side special, Isaac will use Move (a move that pushes his opponents away). As his down special, Isaac will use Earthquake (a move that causes a small Earthquake). As his neutral special, Isaac will use thorn (a move that makes three thorns grow out of the ground).
Isaac is a moderately paced character. As his final smash, he will use Grand Gaia, which causes a reverse meteor shower.
I currently have no information on Isaac's taunts.
Assist Trophies, Pokéballs, and Miscellaneous Items
Missingno. is a Pokémon from the Pokémon Universe. When it comes out of the Pokéball, six of a random item that's currently on screen will appear. If there is no item, Missingno. will have no effect.
The Chain Chomp is an item that originates from the Mario Universe. When grabbed, it will drag the player across the screen, doing damage to the character, but also dealing a lot of knockback to anyone it touches. * indicates this is not a joke character