Spells you can't cast.

[Norm4eva]

Inspired by Evermind and those conditionally free MM cards.  These are test names obviously.

Sneaky Blue

Instant

You may only play -CARDNAME- when you play a spell with UU in its casting cost.
-CARDNAME- is blue.
Draw a card, then discard a card.

Sneaky White

Instant

You may only play -CARDNAME- when you play a spell with WW in its casting cost.
-CARDNAME- is white.
Target player gains 2 life.

Sneaky Green

Instant

You may only play -CARDNAME- when you play a spell with GG in its casting cost.
-CARDNAME- is green.
Put a +1/+1 counter on target creature.

Sneaky Red

Instant

You may only play -CARDNAME- when you play a spell with RR in its casting cost.
-CARDNAME- is red.
-CARDNAME- deals 2 damage to target creature or player.

Sneaky Black

Instant

You may only play -CARDNAME- when you spell a spell with BB in its casting cost.
-CARDNAME- is black.
Target player discards a card from his or her hand.

Over/underpowered?  Could these be more interesting??

[Norm4eva]

Current wording:

Sneaky Blue

Instant

You may only play -CARDNAME- when you play a spell with UU in its casting cost.
-CARDNAME- is blue.
Draw a card, then discard a card.

Sneaky White

Instant

You may only play -CARDNAME- when you play a spell with WW in its casting cost.
-CARDNAME- is white.
Target player gains 2 life.

Sneaky Green

Instant

You may only play -CARDNAME- when you play a spell with GG in its casting cost.
-CARDNAME- is green.
Put a +1/+1 counter on target creature.

Sneaky Red

Instant

You may only play -CARDNAME- when you play a spell with RR in its casting cost.
-CARDNAME- is red.
-CARDNAME- deals 2 damage to target creature or player.

Sneaky Black

Instant

You may only play -CARDNAME- when you spell a spell with BB in its casting cost.
-CARDNAME- is black.
Target player discards a card from his or her hand.

[Matt]

These look a lot like my kicker machine cycle.

[Anusien]

There is a whole lot of rules baggage attached; the best I can think of is "Splice onto cards with WW in their casting cost".  Even so, Matt is right and his wording is much more elegant.

[Norm4eva]

Aw, phooey.  I thought I was onto something.