No, there's no particular reason to suppose an etymological connection between /kuri/ and the other two words.
This /-ri/ ending is very common in mimetic adverbs, and indeed we find the expected related term /mukumuku/ as well. There is no /zuguzugu/ that I'm aware of, but according to the Nihon Kokugo Daijiten there is a dialect word /zugumu/ which means "to be short and fat".
In other words, we know in similar cases that the /-ri/ is an affix and the specific mimetic meaning is carried by the rest of the word. We have strong evidence that this is the case here too. Therefore the most likely hypothesis is that the appearance of /-kuri/ or /-guri/ in these two words is just a coincidence, same as it is in /bikkuri/, /yukkuri/, etc.
However, it is certainly possible that the design of the characters you show was influenced by the similarity of the two words. Even if the word /kuri/ has nothing to do with /zunguri/ etymologically speaking, an illustrator might still notice the similarity of the words (even subconsciously!) and let it influence her work.