Whenever I play with Tilly, or she has her 'mad half hours' (which usually last half a day!) I've noticed that just her tail bushes up when she gets excited and giddy - do other people's cats' tails do this?!

Yep, sounds very familiar. Along with the sideways running. I often think that with these two characteristics they look just like lemurs

Yes! Definately very much like a lemur!!

Yep Oska does this, when he's in that kind of mood and is being chased he also does somersalts to change direction as well as side ways walking

Naomi

My silver boy, Ernie, definitely looks like a lemur when he rushes around with his tail up in the air - we live near a zoo with lots of ring-tailed lemurs and I'm sure he could infiltrate their enclosure with no trouble

Teresa

Yeah my two bengal girls do that also, i think they look like raccoons very funny to watch.