Tricia my oldest cat (Gracie) is 5 and she still get's crazy at times - although not as much as she used to. She's the cat in my avatar. She's huge - weighs about 23 pounds!!

I think the younger one (Tigger) gets her going. He has more energy than she does - plus he's about 12 pounds lighter so I'm sure that helps!!

They just get a "wild hair" sometimes and race around the house - sounds like a herd of horses!