A clingy brother who loves his sister more than the whole wide world, he is willing to do anything to try and make her happy and thoroughly enjoys her company (a little too much personally speaking.) He is very chill towards other people, but when it's his sister he is almost a completely different person. A lot of times to the point where he becomes more of an annoyance to his older sister than anything else.

Since Billy is technically the youngest of the cast, I picture his voice would sound like a slightly younger version of El Tigre. As for the sheer amount of enthusiasm and expressiveness, I leave that category entirely up to you.