There is an officially licensed Mammott plush that plays its Plant Island track when pressing it. However, this track contains a different voice clip that sounds like Matthew Stewart ran out of breath when voicing Mammott. This could be an unused second track? It couldn't be just a broken down voice box, because every Mammott plush contains this sound. What do you think?
I tried to find the cleanest quality version on YouTube. This was the cleanest one. This concept art is also official, by the way.
