Being a little more serious here...
Oh, who do I kid? The substance I'm about to provide will leave me mocked for a few days, but I suppose there are a lot of moms out there like this.
Though my mom does act like an 'adult,' there are random points in time when she starts to... Well, the only term I can find that would be accurate enough for this description is: SPAZZING OUT.
She'll use adorable, sing-song tones, 'tickle torture' the family members around, wrestle with the dog, watch cartoons, and become a total comic book nerd when need be. (Though I have to say she's an even bigger movie nerd, Star Wars to be precise. :O)
My father isn't exactly matured himself. More than 50 and yet he has more comic books than I have files on my computer. Believe me, that's very hard to overcome, with the near insurmountable number of files I have in every folder I posess. Mostly filled with cartoons and sprites, but you get the idea.
The thing is, they're parents. You can't stop them from acting how they want. If you do, chances are they'll get angry and make you miserable, and we all know misery is not the best medicine. :)