A collection of more or less useful functions for legacy versions of WoW (currently TBC 2.4.3, WotLK 3.3.5a, Cata 4.3.4, MoP 5.4.8)
AntiShitter
Toggle with /dr antishitter
Notifies you if there's an ignored player in your party/raid (defaults to on)
AutoPurge
Access submenu with /dr autopurge
Allows you to maintain a list of items to be automatically purged from your bags (defaults to off)
CapShard
Set shard amount with /dr shard XX
Caps the amount of Soul Shards you carry to a certain number. When this is on, any excess shards are automatically deleted (defaults to off)
Guild Ding Notifier
Toggle with /dr gding
Lets your guild know when you level up! (defaults to off)
HonorGoal
Set Honor amount with /dr honorgoal XX
Lets you set an honor point goal and get updates whenever you earn honor (defaults to off)
iLvLUpdate
Toggle with /dr ilvlupdate
Notify you when your average equipped item level changes (defaults to off)
Innervate Notifier
Toggle with /dr innervate
Sends a whisper to the receiving target when you cast Innervate on them (defaults to on)
Monster Emote
Toggle with /dr monster
Emphasizes monster emotes such as "Murloc runs away in fear!", by displaing them in the top error frame (defaults to on)
No Deal
Access submenu with /dr nodeal
Lets you maintain a list of items that the addon will prevent you from selling. Great for things you want to keep, but have a sale value (enchanting rods, Pet Rock, etc)
Party Achievement Notifier
Toggle with /dr partyachi
Posts a notification about your gained achievements to the party chat, for grouping with guild outsiders (defaults to off)
RepTrack
Toggle with /dr rep
Changes your currently watched faction ("display as bar") whenever you gain reputation (defaults to on)
RepAnnounce
Toggle with /dr repa
Shows you a discreet notification window and plays a non-intrusive sound whenever your standing with a faction changes (defaults to on)
RepCalc 
Toggle with /dr repc
Shows you progress to next reputation level whenever you gain reputation with a non-Exalted faction (defaults to off)
Rested Notifier
Toggle with /dr rested
Notifies you when entering or leaving a resting area, showing how much rested XP you've accumulated, if any (defaults to on)
SpiderBurrito
Toggle with /dr spiderburrito
Notifies nearby players when you are afflicted by Web Wrap (defaults to on)
SetRescue
Toggle with /dr setrescue
Automatically buys back items part of an equipment set if sold to a vendor (defaults to on)
These functions have to be activated manually through the command line or by using them in a macro:
Bag Worth
Activate with /dr bagworth
Show the total worth of the items in your bags
Book Club
Activate with /dr bookclub
Add TomTom waypoints for the Higher Learning achievement in Dalaran
Gray
Activate with /dr gray
Purge all gray items from your bags (asks for confirmation first)
LowGray
Activate with /dr lowgray
Purge the lowest value gray item slot from your bags, very useful to click when bags are full to get rid of the slot with the lowest value gray items in it
Pony
Activate with /dr pony. Append raid or party to send a message to those channels
Squeal about who has their Crusader Aura on (can be sent to just you, or to party/raid chat)
Raid Disband
Activate with /dr disband
Completely disband a raid group you are the leader of
Random Pet
Activate with /dr pet
Summon a random pet companion with some snazzy random dialogue to go with it
Silent Random Pet
Activate with /dr spet
Summon a random pet companion without the snazzy random dialogue (boring version)
Skin
Activate with /dr skin
See what the highest level skinnable mob is with your current skill
Speed
Activate with /dr speed
Calculates and outputs your current speed. Useful for finding out which speed buffs/effects stack and what the resulting speed is
- Choose your version:
- Open the downloaded archive
- Enter the "Derpy-master", "Derpy-wotlk" or "Derpy-tbc" folder, and extract the folder named "Derpy" into "WoW Install Folder\Interface\AddOns"
Type /derp, /derpy or /dr into the chat box in-game. This will show you more options, akin to what you can see in the screenshots below.
These screenshots are from the WotLK version of the addon, and may look different under your game version, or have features added or removed.
Bug reports, pull requests, and feature requests are welcome!
In my defense, the slogans for the random pet functions are from 2011, when I originally made this addon, and in dire need of updates (and chemotherapy).