The Origin of the Silver Surfer: Part 2 - S1-E2
Continuity mistake: When the Silver Surfer lands on the platform after Galactus feeds on the planet, he is on the right side (viewer's left) of the platform. After Galactus compliments him on his service, the shot changes and he is suddenly on the opposite side of the platform.
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.