Borrow their eyeliner and then don't give it back.
Snicker when the fat ones go skyclad.
Rearrange their alter.
Clean their "tools."
If they mention Magick, ask them to explain......you never understood that dumb card game.....
Step into that drawn circle and ask them what their doing.
Sharpen that dull knife of theirs.
Claim to be a non-Wiccan witch.
Ask if they can wriggle their nose like in Bewitched.
Put on your best Judy Garland voice and ask "Are you a good witch, or a bad witch?"
Throw water on them and expect them to melt.
Explain how adding "an it harm none" completely misses the point of Thelema. Then explain what Thelema is.
Lend them a copy of Liber OZ.
Take them to a Catholic Mass.
Turn their pentagrams upside down.
Recite good poetry during ritual.
Cast that circle counter-clockwise.
Tell the goddess to put up or shut up during the invocation.
Ask if they can do those things like in that movie...what was it?... oh yeah, "The Craft!"
When they start talking about "the Goddess" start chanting things in Ouranian barbaric or Enochian. Explain later that you have a subconsciously wired bullshit-cut-off switch.
See if they know any Hebrew attributions for, say, tarot. Then ask them why they know.
Ask them who Gerald Gardner was. Ask them which degree rites they've been through. Ask them why they haven't, if it's part of the authentic Celtic tradition. Duck, and remind them about the "an' it harm none" bit.
Talk to their cat. Tell them the cat says it wants human sacrifices.
Scream "KALI YUGA!" when they invoke the Goddess.
Ask them who you have to sleep with in order to get initiated to the 3rd Degree.
Ask why so many Wiccan rituals bare a striking similarity to Golden Dawn rituals.
Half way through a ritual, ask the high priestess to wake you when the sex starts...
Edit their book of shadows, inserting material from one of the assorted Necronomicons or the Satanic Bible.
Ask them to recommend a good book on the subject of Wicca. When they respond, repeat that you wanted a good book on Wicca.
When one tells you that s/he is a Witch, tell them not to be so hard on themselves.
Explain the difference between 'skyclad' and 'houseclad';
Remind them the moon has four phases, not three;
Men - wear amber and jet;
Wear a white rob and hood to the summer solstice. Say your swastika is just a rune.
Worship the devil and call yourself a 'real witch'.
Tell them that the green ray only appeals to people that like having their brain shut down.
Tell them the story about how Gardner coined the phrase 'Blessed be' after he 'hired' a West Country priestess from a local brothel who gasped it during the five fold kiss.
Point out that you can't meaningfully be a Kabbalist unless you're Jewish. No, wait, that's for annoying Hermeticists...
Put fire wood around the maypole.