Non-Human Cannonball

When Non-Human Cannonball dies, roll a six-sided die. If the result is 4 or less, Non-Human Cannonball 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.

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.

Smuggler's Copter

Flying
Whenever Smuggler's Copter attacks or blocks, you may draw a card. If you do, discard a card.
Crew 1 (Tap any number of creatures you control with total power 1 or more: This Vehicle becomes an artifact creature until end of turn.)

Pie-roclasm

Pie-roclasm 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