Anti-fairy magic

 Anti-fairy magic is the ability of anti-fairies to do some similar magic that fairies usually do like flying/floating and shapeshifting. But it's main use is to cause dark magic or bad luck.

Shapeshifting
shapeshifting is one of the things that fairies and anti-fairies do in common. The only difference that fairies and anti fairies do in shapeshifting is that when fairies shapeshift they leave their signature color, while anti-fairies all have the same signature color which is dark blue and black. This is prooved in the epidose "The Gland Plan " when anti-Cosmo shapeshifted into a cow but he dosent turn into green instead his color is dark blue and black.

Poofing
This is also one of the similarities of fairies and anti-fairies. Anti-fairies also has the ability of poofing things or himself/herself from one place to another. The only difference of poofing of fairies anf anti-fairies is that the way fairies poof is "Poof" while anti-fairies' way is "Anti-poof".

Bad luck
This is the main use of anti-fairy magic, to cause bad luck occasionally during Friday the 13th. During Friday the 13th, anti-fairies(some) escape from fairy world and go down to Earth to cause bad luck to someone who commits superstitious beliefs. Usually they poof cats infront of a person or poof ladders to people passing by. That's how they cause bad luck. The anti-fairies' dark magic has no effects on people wearing,holding, or touching things that are a symbol of good luck. This was prooved in the episode "That Old Black Magic " when Timmy's mom and dad where not affected by anti-fairy magic because they are wearing good luck costumes.

Anti Fairy Pregnancy
Anti-fairy pregnancy also uses magic because instead of being pregnant for 9 months, the anti-fairies pregnancy is very fast. Anti-fairy pregnancy is the exact opposite of fairy pregnancy because instead of a male giving birth to the child, it's the female that gives birth. And instead of vomiting purple vomit, anti-fairies vomit butterflies. And instead of painful birth giving, the anti-fairy will feel nothing and actually enjoys it. See this for more information:Anti-Fairy Pregnancy.

Power
The source of all anti-fairy magic comes from The Anti-Big Wand which is the opposite of the big wand. No one is sure how the Anti-Big Wand generates power. But since the Big Wand generates power from human beliefs in fairies, maybe the Anti-Big Wand generates power from humans that are not believing in fairies. The Anti-Big Wand had once drained power because of Foop. He drained power from the Anti-big wand to turn Anti-Fairy World into Care Beary World.

Weaknesses
There are 3 known weaknesses of anti-fairies in the show.

Butterfly net
Just like fairies, anti-fairies' magic cannot be used inside a butterfly net. It is shown in the show When Nerds Collide that anti-fairies are sucked inside a hypercube(which is a cube with a butterfly net on top).

Good Luck Charm
Anti-fairy magic is useless when someone is holding, touching, or wearing a good luck charm such as a 4 leafed clover or a horseshoe facing right side up. This is prooved in the episode"That Old Black Magic" when Timmy's mom and dad where wearing goodluck charms and they are not affected by anti-fairy magic.

Too much Bad Luck
too much bad luck is also anti- fairies' weakness because with too much badluck they are easily tricked. For example is in the episode "that old black magic" when timmy did too much bad luck and there are so many anti-fairies that came to him which then are easily tricked to return to fairy world. Also in the special "When Nerds Collide", Timmy did so much badluck that the fairies that is supposed to be circling the globe had been tricked to go in that place when there is so much bad luck.