Blowing bubbles

[Schfifty]

I was watching some of Sesame Street episode #3155 on YouTube, and there's a scene where Zoe starts blowing bubbles. I've been wondering about this for a while, and haven't really found a definite answer, but how are they able to do this trick? There's a later instance in #3877 where Elizabeth blows bubbles as well.

My guess is that either: A) There's a button on the bubble-blower that the mouth pushes, or B) the blower is remote-controlled. Are there any other possible ideas?

 

[Detritusarisen]

It looks like there's an air hole in the mouth somewhere that she holds the bubble pipe up against. Judging by the cut they switched her out for the air model when she starts.