X-Men

When telling Quicksilver where Magneto is every year at this time, High Evolutionary's "teeth" are red.

Wolverine's mask is colored yellow where it should be black, when Xavier tells him to follow Magneto.

The magnetic bonds on Wolverine's legs are visible through the console over his lap in one shot.

The babies in Bova's arms switch places between angles. In close-ups, the blue blanketed one is in her right arm, pink the left, and longer-away shots have it the opposite.

Wundagore is misspelled "Wundargore" on the on-screen title, despite pronounication otherwise.

When first meeting the High Evolutionary, Scarlet Witch's headpiece is colored pink in several shots.

When saying "the mutant who did this", Quicksilver's neck is colored blue.

When his hands are cuffed, Quicksilver fails to make use of his super-speed to escape.

Quicksilver's upper section's movements don't match his lower body when trapped in amber and talking to Magneto.

Prior to capture, Magneto is wearing civilian attire. Once in the citadel, he's got his full costume on.

When hit by Magneto's blast, Wanda doesn't have the energy whip in her hand.

Forge's head vanishes from the transmission when his signal is interrupted, yet the background from where he's calling from remains!

The Hummingbird is just the Starjammer's ship repainted black.

Django Maximoff's eyebrows switch from white to gray when he's first shown.

The scene where Xavier remembers forming the X-Men shows the team at various points in their history: Wolverine (spy gear, first-appearance style costume, current), Iceman (as a boy, then snow-style), Beast (a boy, school uniformed normal-form X-Man, current), Cyclops (as a boy, school uniformed, current), Jean Grey (as a girl, school uniformed, current), Angel (as a boy, school uniformed, current Archangel form with his white and blue Angel costume), Rogue (her runaway outfit, Brotherhood of Mutants outfit), Gambit (flashback outfit, current costume with no coat, then with), Jubilee (casual attire twice, current), and Storm (street thief, first costume, current).

Cameos in Xavier's dream world include (aside from the regular X-Men) all of X-Factor, Lilandra, Nightcrawler, Angel, Morph, Iceman, and Magneto.

Rogue and Gambit appear in this episode only as mental illusions, and neither speak.

Sabretooth & Mr Sinister appear as (speaking) astral illusions.

Similarly, Wolverine is on top of his sheets in the first shot of him sleeping, and the next he's under the covers.

Xavier is lying on top of his sheets in his bed in the infirmary when he's helped to sit up, but the angles switch, and he's under them.