Devil K. Nevil

Haste
When Devil K. Nevil enters, jump it over any number of creatures. If it clears those creatures, put that many +1/+1 counters on it. (You can see a jumping demonstration at DevilKNevil.com.)

Celebr-8000

At the beginning of combat on your turn, roll two six-sided dice. For each result of 1, this creature gets +1/+1 until end of turn. For each other result, it gains the indicated ability until end of turn. If you rolled doubles, it also gains double strike until end of turn.
• 2 — menace
• 3 — vigilance
• 4 — lifelink
• 5 — flying
• 6 — indestructible

Non-Human Cannonball

When this creature dies, roll a six-sided die. If the result is 4 or less, this creature deals that much damage to you.

Pietra, Crafter of Clowns

Haste
Robots you control get +1/+1.
{R}{W}, {T}, Tell a joke you haven't told this game to someone outside the game: Create a 1/1 white Clown Robot artifact creature token. If that person laughed, the token gains haste until end of turn.

Starlight Spectacular

Parade! — At the beginning of combat on your turn, choose creatures you control one at a time until each creature you control has been chosen. Each of those creatures gets +1/+1 until end of turn for each creature chosen before it. (Places everyone! The first creature in line gets +0/+0.)

Nearby Planet

Rangeling (This card is every land type, including Plains, Island, Swamp, Mountain, Forest, Desert, Gate, Lair, Locus, and all those Urza's ones.)
This land enters tapped.
When this land enters, sacrifice it unless you pay {1}.

Pie-roclasm

This creature deals π damage to each non-Clown creature. (How to calculate π isn't important. It's a smidgen more than 3.)

Omniclown Colossus

Affinity for Clowns (This spell costs {1} less to cast for each Clown you control.)
Trample

Omniclown Colossus // Pie-roclasm

Circuits Act

Roll three six-sided dice. For each different result, create a 1/1 white Clown Robot artifact creature token.

Assembled Ensemble

Vigilance
Assembled Ensemble's power is equal to the number of Robots you control.
Whenever you cast a spell with an artifact creature in its art, create a 1/1 white Clown Robot artifact creature token.

Impounding Lot-Bot

When this creature enters, you may say "INCARCERATE!" in a robot voice. If you do, exile another target artifact or enchantment until this creature leaves the battlefield.

Goblin Cruciverbalist

Haste
When this creature enters, create a colorless artifact token named your choice of A, E, I, O, or U.
Whenever this creature attacks, using the first letters of the names of permanents you control, spell a word you haven't spelled this game. It gets +1/+0 until end of turn for each letter in that word.

Surprise Party

When this enchantment enters, yell "Surprise!" and put onto the battlefield any number of printed Clown Robot tokens that aren't touching each other, that you hid on the battlefield before you cast this enchantment, and that weren't spotted by an opponent before you cast this enchantment.
Robots you control get +1/+0 and have vigilance.

Clown Car

When this Vehicle enters, roll X six-sided dice. For each odd result, create a 1/1 white Clown Robot artifact creature token. For each even result, put a +1/+1 counter on this Vehicle.
Crew 2

Mountain

Juggletron

Trample
Whenever this creature attacks, you may put an art sticker on it.
This creature gets +3/+0 for each item in its art that's not touching Juggletron, another item, or the card frame.

Ticking Mime Bomb

When this creature enters, without speaking or indicating any specific creature, pantomime to a person outside the game, then they choose a creature you don't control. This creature deals damage equal to twice the number of Robots you control to the chosen creature.