YAY, thats great! I'm glad you've taught Lily a trick, I remember I felt great when I taught Arthur his trick, it is very simple, but when friends come round who think rats are nasty it seems to impress them.
I think that you could easily teach them a 'turn' or 'spin' trick, all you have to do is get some treats they really like, make sure they are on the floor/bed, not on your lap because that was really annoying with Arthur, if I called him over he would bounce straight onto my lap, but he got grumpy when I put him on the floor lol
Anyway... hold the treat above their head and lead them around in a circle, whilse saying turn or spin if you prefer. Keep on repeating this, until they get quicker and professional at it lol, but make sure you keep doing the whole turn gesture, leading them round. Once they have that sorted, try holding the treat above their head and just make circle movments with your hand, and say turn or spin at the same time, keep doing this until they get that sorted and I'm sure it won't be long before you don't need to give them any clues and they just do a turn on command
I love that trick, once I have even seen Arthur do it in his free-range time as if he was practicing LOL
BTW: They can get lazy with it and after a while they might start doing half-turns abd expect a treat, try to stop yourself from giving them a treat for doing a half turn because they'll carry on and think it's okay, just ask them to do it again and if need be, lead them round in a whole circle, than give them a treat