Civilized Scholar, and its transformed version Homicidal Brute, were inspired by R. L. Stevenson novel, Strange Case of Dr Jekyll and Mr Hyde.

Invisible Stalker was inspired by H. G. Wells novel, The Invisible Man.

Uktabi Kong's art depicts a couple of monkeys expecting a child, after their mating in Uktabi Orangutan.

Flaxen Intruder was inspired by the fairy tale Goldilocks and the Three Bears.

Beebles are tiny, playful creatures created by Jeff Miracola in the 90's. They first appeared on the cover of The Duelist #22 (1998).
Over the years, they appeared on many cards, almost all illustrated by Jeff Miracola:

• Equilibrium
• Nausea
• Wizard Mentor
• Donate
• Topsy Turvy
• Sauté
• Frantic Search (Urza's Legacy)

Caller of the Untamed's art from the Conspiracy: Take the Crown set, by Iain McCaig, was the cover of Spectrum #24.

"Ach! Hans, Run!" and Saffi Eriksdotter were both inspired by Lhurgoyf's flavor text. The same Hans is mentioned in Revenant's flavor text (Stronghold).

Emergence Zone and Ravnica at War (War of the Spark) show the same scene from two different points of view.

The card Louvaq, the Aberrant looks stickered on is Roalesk, Apex Hybrid.

The card Personal Decoy looks stickered on is Dovin, Grand Arbiter.

The name and text on Frenetic Sliver are references to Frenetic Efreet.

The cards on Johnny, Combo Player's Unhinged and Unsanctioned arts are not the same.

On the Unhinged version, from nearest to farthest, there are Soul foundry, Recycle, Clock of Omens, Urza's Contact Lenses, Cadaverous Bloom and Mind over Matter.
On the Unsanctioned version, there are Krark-Clan Ironworks, Genesis Chamber, Myr Retriever, Faithless Looting, Force of Will (to be confirmed) and a unknown (yet) card.
Krark-Clan Ironworks, Genesis Chamber and Myr Retriever were already mentioned in the Unhinged version's flavor text.

The textless Plains from Amonkhet and Hour of Devastation, along with both versions from Archenemy: Nicol Bolas, all depict the same place with Bolas horns in the background.

The textless Islands from Amonkhet and Hour of Devastation, along with both versions from Archenemy: Nicol Bolas, all depict the same place with Bolas horns in the background.

The textless Swamps from Amonkhet and Hour of Devastation, along with both versions from Archenemy: Nicol Bolas, all depict the same place with Bolas horns in the background.

The textless Mountains from Amonkhet and Hour of Devastation, along with both versions from Archenemy: Nicol Bolas, all depict the same place with Bolas horns in the background.

The textless Forests from Amonkhet and Hour of Devastation, along with both versions from Archenemy: Nicol Bolas, all depict the same place with Bolas horns in the background.

Plains from Innistrad and Avacyn Restored, illustrated by Adam Paquette, depict the same place before and after the return of Avacyn.

Plains from Innistrad and Avacyn Restored, illustrated by Jung Park, depict the same place before and after the return of Avacyn.

Plains from Innistrad and Avacyn Restored, illustrated by Eytan Zana, depict the same place before and after the return of Avacyn.

Islands from Innistrad and Avacyn Restored, illustrated by James Paick, depict the same place before and after the return of Avacyn.

Islands from Innistrad and Avacyn Restored, illustrated by Adam Paquette, depict the same place before and after the return of Avacyn.

Islands from Innistrad and Avacyn Restored, illustrated by Jung Park, depict the same place before and after the return of Avacyn.

Swamps from Innistrad and Avacyn Restored, illustrated by James Paick, depict the same place before and after the return of Avacyn.