The sound he makes suggests that they will be going for a higher-pitched baby voice for the reborn character.
Also, he’s wearing this adorable leather jumpsuit that we were able to see in the longer San Diego Comic-Con cut of the Guardians of the Galaxy Vol. 2 footage.
There was rapid-fire shots of the different members of Peter Quill’s team, including Gamora brandishing a badass sword, and concluding with our first look at Baby Groot (Vin Diesel) in action.