Duel Identity, Part I - S1-E29
Other mistake: When Yugi summons Summoned Skull, the defence points are displayed as 2300. Summoned Skull has 1200 defence points every other time it is shown. (00:09:07)
Buttercrush / Fuzzy Logic - S1-E4
Continuity mistake: When Buttercup punches a hole in the wall to see her sisters are being lowered into lava, the hole's initially quite small. In the next shot, the hole is noticeably bigger.
The Origin of the Silver Surfer: Part 1 - S1-E1
Continuity mistake: When Norrin Radd is placing the Kree and Skrull weapons on the rock, he is lying them down on the edge of the rock furthest from him. When the shot changes, he places them down on the edge nearest to him.