That's because being bubbly has nothing to do with ENFPs.
There is a popular typology site or book (I forget which one--maybe it's from Please Understand Me) that says something like "when ENFPs talk, they're like a fountain bubbling over, their mouths trying to keep up with with the rapid thoughts and ideas, etc."
Somewhere along the line, people interpreted this as ENFPs being bubbly, when that's not what it meant at all.
And some typology sites list Ariel from Disney's The Little Mermaid as an ENFP, which, in my opinion, confuses the issue even more.
Then there is the "silly switch" concept, being extremely goofy at times, which I think is true of ENFPs, but all this stuff together gets all twisted into the false idea that ENFPs are generally bubbly, cutesy, and giggly.