I think I'll just repeat what I said in the chat:

You have two teams of wizards. In order to make a move you must change shape into a creature or thing that beats, defeats or otherwise trumps whatever the other side has just changed into. So you might get a sequence like

Wizards: Elephant
Witches: Mouse
Wizards: Cat
Witches: Dog
Wizards: B - A - T - H
Witches: Telephone

at which point I have to admit I'm stumped so presumably the witches win that round.

CdM
FIFA
Olive Drab
FOFUM
Olive
A beanstalk
Goldenrod
Agent Orange
all
Azure
Mr White
Puce
Professor Plum
CdM
Green
Lead piping in the kitchen
Olive
Health and Safety
Puce
Common sense
Goldenrod
An embedded hyperlink
aqua
Your nephew, who despite being only eight knows more about computers than you ever will
all
Azure
Napalm - It's the only language they understand.
Puce
Fuel-Air Explosives
aqua
The cold vacuum of space
CdM
Green
The total perspective vortex
Olive
Zaphod Beeblebrox
Puce
Ace Rimmer. What a guy.
Olive
Victory for Simons Mith I feel.
Puce
Thank you. I was quite pleased with that one.
Marmite
aqua
Dynamite
all
Azure
Jamiroquai
Tuj
Lime
A ten-tonne lime
Puce
The invincibility of the ten-tonne lime is something that surprises me, but I haven't thought of a satisfactory counter. Time to award this one to Tuj … and put the game into storage ready for next time.
Audience
*shouts, screams, generally goes wild for Simons Mith*
Puce
… An eleven tonne lime. Dammit, l'esprit d'escalier rides again.
aqua
All I could think of was Lyme disease.
Tuj
Lime
A million gallons of G&T? But that'd just be getting silly, eh?
goldenrod
I'm a tad rusty in my French. I translate l'esprit d'escalier as "the phantom staircase". This is obviously a cunning metaphor for something to do with eleven tonne limes (or perhaps twenty-one tonnes of limes), but the meaning escapes me.
L'esprit d'escalier
It's an idiom for thinking of some witty retort just after the last moment.
#66FFCC
Isn't it "the spirit of the staircase?"
Puce
Let's start a new one. An eleven tonne lime
An industrial lime-squeezer
Blue
A hell of a lot of Mojito Mix
puce
Prohibition
Blue
President Franklin Roosevelt
aqua
A Fourth Term
Tuj
Lime
The Fourth Estate
#66FFCC
The Saudi Monarchy
Lime
The taliban.
#66FFCC
Bacon.
Blue
A London Cabbie
Blue
This is the end of the line. There is no more.