Exit Through the Grift Shop

Yell "Who wants a souvenir?" and announce the name of a nonland card in your graveyard. Each player in an Un-game who can hear you may bid life. You start the bidding at 0. The high bidder loses life equal to the high bid. They copy the card and may cast the copy without paying its mana cost. If you didn't win the bid, you gain life equal to the high bid and create that many Treasure tokens.

Super-Duper Lost

Put target creature into its owner's library just beneath the top X cards of that library, where X is the number of doors you can see from your seat.

Tunnel of Love

Visit — Choose an opponent. They choose a creature they control, then you choose a creature you control. You may exile the chosen creatures. If you do, return them to the battlefield under their owners' control at the beginning of the next end step. Otherwise, the chosen creatures fight each other.

Vedalken Squirrel-Whacker

As Vedalken Squirrel-Whacker enters, roll a six-sided die twice. Its base power becomes the first result and its base toughness becomes the second result.
If you would roll one or more six-sided dice, instead roll them and you may exchange one result with Vedalken Squirrel-Whacker's base power or base toughness.

Standard Procedure

{1}, Reveal Standard Procedure from your hand: Choose an instant or sorcery card with mana value 3 or less currently legal in the Standard format. Standard Procedure becomes that card until end of turn.

Swinging Ship

Visit — After the first combat phase this turn, there's an additional combat phase. At the beginning of that combat, untap all creatures that attacked this 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

Omniclown Colossus // Pie-roclasm

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.

Goblin Girder Gang

Reach
Whenever you roll a die, if the result isn't stored on Goblin Girder Gang, you may store that result on it. When you do, Goblin Girder Gang deals 1 damage to any target without a hat.
Goblin Girder Gang gets +1/+0 for each result stored on it.

Sword-Swallowing Seraph

Flying, vigilance
When Sword-Swallowing Seraph enters, you may put a name sticker on a nonland permanent you own.
{1}{W}, {T}: Put a +1/+1 counter on another target creature with a name sticker on it. Activate only as a sorcery.