There is some fun to be had here for younger audiences especially, but this is essentially a few episodes stitched together without much added

Honestly, a title like Plankton: The Movie is about as difficult to evaluate as any movie that comes down the Hollywood pike or, in this case, washes up on its shores. Not because it’s a spin-off of SpongeBob Squarepants – or at least, not because there is anything inherently wrong with a spin-off movie of such a durably silly and enjoyable kids’ franchise – but because it often feels somewhere to the side of genuine feature-film status. In executive terms, it is more like content.

Lengthwise, Plankton does qualify as a feature, though its official runtime of nearly 90 minutes doesn’t really do justice to the fact that it runs closer to 75 when you take out the extensive end credits. Anyway, that’s not a problem; there’s a rich tradition of animated movies aimed at kids not overstaying their welcome, and Plankton himself is such a little guy.