I checked out your devlog and I would lean more on the side that theyre a little too cute. imo, I think the shape/proportions of the characters are fine. Its the eyes and the color palette that are giving them their "cutesy" look. theyre pretty close to FF saturated colors from the looks of it. I think bring them down to somewhere between AA-DD you'll get a slightly more ominous look. Also you have the added bonus of having really white/light gray backgrounds so I think you can afford to make the characters a little darker.
About the eyes, or more so the face, I dont have a specific suggestion in mind but 2 beady eyes with no mouth/nose/other facial features makes it look cute. I just wrote that I didnt have a suggestion, but an idea just popped up to just remove the eyes entirely? you might have to reshape the face a bit to make it look right, but it might look less cute/more creepy if they had a blanker expression.
Thanks everyone - that was really helpful. I've more or less followed CaLooch' suggestions and I'm pleased with the look (even if I am still a terrible animator
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Updated DEV log with GIF's
http://forums.tigsource.com/index.php?topic=47397.msg1150336#msg1150336