Oh you're right, I interpreted that dash in the leftmost bubble as a pause dash rather than a continuation dash (though does Japanese use either of those? I understand it as "repeat the previous vowel", but I am a novice).

Chat GPT also suggests that it might just be meant as a cute sound rather than having any literal meaning.

Also, do Japanese make puns based on sounds that can be interpreted in different ways depending on where one word is assumed to end and another begin, or mixing the end of one word into the start of another (eg using the n as both the end of "goman" and the start of "nyan")?