Good Cop, Bad Cop: an original card game by David Parlett

"Alliance games" is what I call those where you play in partnerships but partners change from deal to deal. I've always preferred them to fixed-partnership games. Not everybody does, though some of the most classic games were of this type, notably Quadrille. Charles Lamb's view of this arrangement may be gleaned from the words he put into the mouth of his creation the Whist-loving Sarah Battle: "She despised the chance-started, capricious, and ever fluctuating alliances of [Quadrille]. The skirmishes of quadrille, she would say, reminded her of the petty ephemeral embroilments of the little Italian states, depicted by Machiavel; perpetually changing postures and connexions; bitter foes to-day, sugared darlings to-morrow; kissing and scratching in a breath..." (Charles Lamb, "Mrs Battle's Opinions on Whist", in The Essays of Elia, 1823.)

I nearly called this game "Sugared Darlings", but times change...

Cards: 54, including two Jokers. Cards rank from high to low AKQJ1098765432 in each suit.
Deal: Deal two cards face up to the table. The suit of the uppermost card is the trump suit (good cop), the suit of the other is the penalty suit (bad cop). If they are both the same suit it plays both roles simultaneously. If one turn-up is a Joker, the suit of the other is both good and bad. If both are Jokers, shuffle them back into the pack and turn up the next two. From the rest of the pack deal 13 cards each, in ones.
Object: First, to win tricks but avoid taking in penalty cards. Second, to find out who your partner is. The two players holding Jokers are the good-cop partners and their opponents are the bad-cop partners, but their identities must not be revealed before they become known by the play of Jokers. If one player has both Jokers, or one Joker when the other is a turn-up, that player plays the lone good cop against a partnership of three bad cops.
Play: The player at dealer's left leads to the first trick. You must follow suit if you can but may otherwise play any card. The Jokers start off by representing either of the two turn-ups. The first time a Joker is played, its holder must state which turn-up it is, and exchange it for that turn-up. The second Joker then automatically represents the remaining turn-up, and must be exchanged for it when played. Note that if the suit led to a trick is that of either turn-up and you have none of that suit in your hand but do have a Joker, then you must use that Joker and thereby follow suit. It is permissible to lead a Joker to a trick in order to clarify partnership identities, and of course it must represent one of the turn-ups.
Scoring: Each partner scores 10 points for each trick won by their side and subtracts from this the square of the number of cards they contain of the bad-cop suit. For example, if they win nine tricks containing seven bad-cop cards, each partner individually scores 41 (90 minus 49), while each opponent will score 4 (40 for tricks minus 36). If one person was playing solo, the soloist alone (not each opponent) scores 20 per trick minus the square of the number of bad-cops cards taken. Note that it is possible to score a negative number. For example, if one side wins all 13 tricks, and therefore all 13 bad-cop cards, their score will be minus 39 (130 less 169), and their opponents will score zero.
Game: Play four or eight deals, or up to a target score of, say, 250.