How would taking the batteries out help you? And there ARE universal characters, and are the "OTHER" family. They come from the teens Hoshitamatchi or Hikotchi. Once you have one of them, get your fashion points high, and you'll have Mametchi.
And as for lilylovestamas, you most likely got UraMametchi, since crackertchi evoles into UraMaetchi. Was it your second generation?
Another option is doing what kuchipatchi love said, and doing the matchmaker until she brings a Mametchi, Kuchipatchi, or Gozarutchi. Then on the next generation, raise your fashion, and you should get Mametchi.
So yes, it IS possible.
Hope I helped!
~Zack//