Most of the cards in
Planar Chaos were inspired by cards from Magic's past.  
Aeon Chronicler refers to Maro and is the only Avatar in Planar Chaos.
Aether Membrane is the only Wall in Planar Chaos. Its abilities refer to Whip Vine and Wall of Tears.
Akroma, Angel of Fury is the only creature in Planar Chaos with protection from blue or that can't be countered. It refers to Akroma, Angel of Wrath and is the only rare creature in the set with morph.
Ana Battlemage refers to Anavolver and Thornscape Battlemage.
Auramancer's Guise refers to Rabid Wombat.
Battering Sliver refers to Horned Sliver.
Big Game Hunter refers to Reprisal, and is the only  assassin in Planar Chaos.
Blightspeaker refers to Cackling Imp and Defiant Falcon.
Body Double refers to Clone and Zombify.
Braids, Conjurer Adept refers to Braids, Cabal Minion.
Boom//Bust refers to Tremble and Armageddon.
Cautery Sliver refers to Goblin Legionnaire.
Circle of Affliction refers to Story Circle.
Cradle to Grave refers to Dark Banishing and Premature Burial.
Crovax, Ascendant Hero refers to Ascendant Evincar. Third ability refers to Selenia, Dark Angel.
Darkheart Sliver refers to Dark Heart of the Wood.
Dash Hopes refers to Counterspell and Molten Influence.
Dawn Charm refers to Holy Day, Death Ward and Gilded Light.
Dead//Gone refers to Shock and Unsummon.
Deadly Grub refers to Deadly Insect.
Deadwood Treefolk refers to Gravedigger and is the only treefolk in Planar Chaos.
Detritivore refers to Terravore and Skyshroud War Beast , and is the only lhurgoyf in Planar Chaos
Dichotomancy refers to Mimeofacture
Dismal Failure refers to Dismiss.
Dormant Sliver refers to Jungle Barrier.
Dreamscape Artist refers to Harrow.
Dust Corona is a mirror of Web.
Enslave refers to Control Magic.
Erratic Mutation refers to Erratic Explosion and Unstable Mutation.
Evolution Charm refers to Lay of the Land, Raise Dead and Flight.
Extirpate refers to Eradicate and Word of Command (art). 
Fatal Frenzy refers to Berserk.
Firefright Mage refers to Shriek of Dread.
Frenetic Sliver refers to Frenetic Efreet.
Fury Charm refers to Shatter and Vitality Charm.
Ghost Tactician refers to Scare Tactics.
Hammerheim Deadeye refers to Wing Snare.
Heroes Remembered refers to Blessed Wind.
Hunting Wilds refers to Skyshroud Claim
Imp's Mischief refers to Deflection and Withering Boon.
Intet, the Dreamer refers to Dromar, the Banisher. 
Jedit Ojanen of Efrava refers to Jedit Ojanen and Cat Warriors. It is the only card of the Alternate Legendary Creature cycle (see Cycles section on set's page) to be based on a multicolored creature.
Jodah's Avenger is the only creature in Planar Chaos with Protection from Red in its text box. It refers to Urza's Avenger and is also the first card to refer to Jodah.
Kavu Predator refers to Kavu Titan and is the only Kavu in Planar Chaos.
Life and Limb refers to Living Lands. 
Magus of the Arena refers to Arena.
Magus of the Bazaar refers to Bazaar of Baghdad.
Magus of the Coffers refers to Cabal Coffers.
Magus of the Library refers to Library of Alexandria.
Magus of the Tabernacle refers to The Tabernacle at Pendrell Vale.
Mantle of Leadership refers to Herd Gnarr.
Midnight Charm refers to Feast of Flesh, Hope Charm, and Ivory Charm.
Mire Boa refers to River Boa and is the only Snake in Planar Chaos.
Mirri the Cursed refers to Mirri, Cat Warrior and is the only Vampire in Planar Chaos.
Muck Drubb refers to Blood Pet (art only). 
Necrotic Sliver refers to Vindicate.
Needlepeak Spider refers to Giant Spider and is the only Spider in Planar Chaos.
Numot, the Devastator refers to Darigaaz, the Igniter.
Oros, the Avenger refers to Treva, the Renewer.
Pallid Mycoderm is the first white Fungus.
Pongify refers to Afterlife and also depicts a Torchling-like barbarian as the subject of the spell. 
Poultice Sliver refers to Crypt Sliver.
Pouncing Wurm refers to Pouncing Kavu.
Radha, Heir to Keld is the only legendary creature in Planar Chaos to not be part of a cycle.
Rebuff the Wicked refers to Avoid Fate and Shelter.
Reflex Sliver refers to Heart Sliver.
Retether refers to Replenish.
Ridged Kusite's name is an anagram of the spell it shapes, Guided Strike, which is appropriate given that it is the creature featured on the original version of that card. Weatherlight 
Riftmarked Knight is the only creature in Planar Chaos with Protection from Black or flanking. It refers to White Knight and Black Knight.
Roiling Horror is the only black card with Suspend in Planar Chaos. It refers to Serra Avatar.
Saltblast refers to Desert Twister.
Saltfield Recluse refers to Sanctum Custodian. 
Serra's Boon is a mirror of Phyrexian Boon. 
Shade of Trokair refers to Hoar Shade and is the only Shade in Planar Chaos.
Sophic Centaur's ability is a colorshifted Gerrard's Wisdom and is the only Centaur in Planar Chaos.
Spellshift refers to Polymorph; whereas Polymorph affects creatures, Spellshift affects instant and sorcery spells.
Spitting Sliver refers to Talon Sliver.
Stingscourger refers to Man-o'-War. 
Synchronous Sliver is the only member of the common Sliver cycle (see Cycles section on set's page) to have an ability not appearing on a Sliver from a past expansion.
Temporal Extortion refers to Time Walk.
Teneb, the Harvester refers to Crosis, the Purger.
Timbermare refers to Thundermare. Timbermare was made as a tribute to the wife of longtime Magic writer Jamie Wakefield who had sadly passed away from cancer. Jamie always referred to her as his “lovely Mare”.  
Torchling refers to Morphling.
Treacherous Urge refers to Threaten.
Truth or Tale refers to Fact or Fiction.
Urborg, Tomb of Yawgmoth is the only colorless card and only land in Planar Chaos. Its ability is a reference to Blanket of Night.
Utopia Vow refers to Pacifism and Utopia Tree.
Venarian Glimmer refers to Distress and Venarian Gold.
Voidstone Gargoyle refers to Meddling Mage and Pithing Needle. Vorosh, the Hunter refers to Rith, the Awakener.
Blood Knight is a mirror of Black Knight; it also refers to White Knight. Blood Knight was the placeholder name for the Scourge set's Silver Knight.
Calciderm is the only timeshifted member of the vanishing cycle (see cycles section on the set page); it is a colorshifted Blastoderm.(with Vanishing 4 rather than Fading 3, usually producing about the same lifespan).
Damnation refers to Wrath of God in art, artist, and mechanics.
Essence Warden refers to Soul Warden in art.
Fa'adiyah Seer refers to Sindbad. Its name refers to Fa'adiyah the forest on the plane of Rabiah.
Hedge Troll is a mirror of Sedge Troll.
Keen Sense refers to Curiosity. Keen Sense represents a moment in the Exodus storyline that could only have occurred had things transpired between Mirri, Crovax, and the dark angel Selenia very differently.
Ovinize refers to Humble. The sheep art also refers to Ovinomancer, who has the ability to turn creatures into sheep.
Piracy Charm is the only timeshifted member of the Charm cycle (see Cycles section on set's page) and refers to Funeral Charm.
Porphyry Nodes refers to Drop of Honey. Porphyry Nodes is a near-anagram of " Drop of Honey." This hearkens back to a time when Magic names used near-anagrams more often. For example, " Onulet" is a near-anagram of " Soul Net," so named because of its life-gain ability.
Primal Plasma refers to Plasma Elemental in art and Primal Clay in mechanics and is the only card timeshifted from an artifact.
Prodigal Pyromancer refers to Prodigal Sorcerer in ability and flavor text.
Riptide Pilferer refers to Headhunter. Riptide Pilferer depicts a merfolk spy lurking under the docks of the Riptide Project, the wizards' laboratory off the coast of Otaria where cephalid and human mages traded secrets and replicated slivers.
Seal of Primordium refers to Seal of Cleansing (mechanic, artist, flavor text) and Gauntlet of Power (art).  Vampiric Link refers to Spirit Link in mechanic, artist, and art.
Matt Cavotta (February 22, 2007). " ". Time Spiral Magic Museum - Planar Chaos Exhibit . Wizards of the Coast. magicthegathering.com
Mark Rosewater (January 22, 2007). " The Great Mix-Up, Part I". . Wizards of the Coast. magicthegathering.com
Mark Rosewater (February 05, 2007). " The Great Mix-Up, Part II". . Wizards of the Coast. magicthegathering.com
Wizards of the Coast (February 22, 2007). " Reprisal Rebel". . Wizards of the Coast. magicthegathering.com
Wizards of the Coast (February 20, 2007). " Extirpate Sketches". . Wizards of the Coast. magicthegathering.com
Aaron Forsythe (January 19, 2007). " The Rebirth of Cool". . Wizards of the Coast. magicthegathering.com
Wizards of the Coast (April 03, 2007). " Limb Art Gets New Life". . Wizards of the Coast. magicthegathering.com
Wizards of the Coast (February 01, 2007). " Art of the Alternate Past". . Wizards of the Coast. magicthegathering.com
Wizards of the Coast (April 10, 2007). " Pongified Barbarian". . Wizards of the Coast. magicthegathering.com
Wizards of the Coast (November 20, 2008). " What's a Kusite?". . Wizards of the Coast. magicthegathering.com
Wizards of the Coast (April 05, 2007). " Saltfield Time Wizard". . Wizards of the Coast. magicthegathering.com
Wizards of the Coast (March 28, 2007). " Double Boon". . Wizards of the Coast. magicthegathering.com
Wizards of the Coast (February 08, 2007). " Stingscourger's Sting". . Wizards of the Coast. magicthegathering.com
Mark Rosewater (March 03, 2016). " Can i ask for sone trivia on Timbermare?". Blogatog. Tumblr.
Jamie Wakefield (January 8, 2007). "Official Planar Chaos Preview - Timbermare!". StarCityGames.com
Wizards of the Coast (March 21, 2007). " Seal of Primordium". . Wizards of the Coast. magicthegathering.com