So I am going to have an npc wizard in my campaign who will take a liking to the party. Unfortunately for the pcs he will have an odd sense of humor, and considers things like drugging his friends and selling them into slavery a practical joke. So far I have come up with that and framing them for a crime. Does anyone have any other ideas along these lines for my wizard to mess with my pcs?
I am going to start with the assumption that your players are ok with a little railroading. Being sold into slavery is the kind of thing that will drive some players crazy.
That being said I would start small.
1. Spread rumors that the PC's are evil or traitors or criminals, demons in disguise, whatever...suddenly their favorite establishments don't want to do business with them.
2. Bribe officials to harass them...whenever they enter or leave town...have they paid their taxes?...what about guild fees, etc.
3. Have stolen items end up in their rooms or saddle bags, etc.
4. Pay the town drunk to give you some of his blood and then leave town. Use blood to incriminate PC.
5. Pay a bard to sing songs about the "exploits" of the PC's all over town. Exploits should make PC's look horrible.
6. Are any x-girlfriends available to claim pregnancy and a PC is the father?
I'm all for roguish recurring NPC "problem children," but I would use this trope sparingly if I were you. Personally, I think you don't need more than you already have to make them hate this guy (and possibly you, as well).
I see it being a love hate thing. He rewards them really well, and they end up discovering valuable info during the course of their prank. The wizard is doing it intentionally to feed them info in his own eccentric way but the pcs won't know this. I'm looking to add 1... maybe 2 more quality hooks with this character.
Here are some possible adventure ideas related to what I said above.
1. The PC's new "evil" reputation encourages whatever evil organization you want to try and recruit them.
2. The wizard bribing officials to harass the party leads them to corruption in the guard, government, knightly order, etc.
3. The items are stolen from very bad people and they want them back that draws the party into conflict with whoever the NPC wants.
4. The party has to find the drunk to prove their innocence and that can lead them wherever you want the party to go.
5. This one is just fun but could serve same purpose as #1.
6. The x-girlfriend is a princess whose father just died. This makes the baby the heir to a contested thrown and a PC the father. Assassins soon follow.