We play a bunch of games, too many to list here, but there are a few we've been playing more than others lately. Maggie's favorite is what she calls Broom -- when Mom pulls out the broom to sweep up the scattered litter along "kitty litter lane" Maggie will hide behind the nearby door and try to get the broom bristles from underneath the door. This one looks fun, but the door gets pushed out when I try to get behind it.
The other game we like to play we call Stare (sometimes we call it Where's the Bug?, but it's essentially the same game) -- the premise is very simple, you sit still and stare at a very specific spot, usually the center of the ceiling or where the wall meets the ceiling. This will make Mom and Dad walk around in circles staring at spots on the ceiling. It's very funny because they look silly. To keep them interested in the game, you may want to actually spot a bug on the ceiling every once in a while (like I did tonight) so the threat stays real. Get your siblings to play along with you and it's even more fun because then Mom and Dad get really curious ("What are they all looking at?") ... good fun for all and it encourages Mom and Dad to get some exercise.