Pets that are a higher level than you gradually untame over time, though they will always turn peaceful when they untame unless you have abused them.

Solve the problem of pets wasting their hard-trained apport by picking up and dropping objects randomly all over the dungeon, by triggering them only to use it when the hero plays any instrument (or maybe any non-magical instrument). Bonus points if the player can train the pet by playing an arbitrary sequence of notes (chosen by the player) on tonal instruments.

Pets treat the entrance space to shops, or shop-owned items in the shop, as cursed, as a measure against using them to easily steal items. The latter is more likely to be effective, since the first method can be defeated without too much difficulty with a magic whistle.

Stone of pacification, which when you carry it in open inventory prevents your pets from attacking peaceful monsters. (It does not affect hostile monsters, nor does it stop pets from attacking hostile monsters.)

Pets should not attack coaligned priests.

Pets that know they have reflection (from an amulet, spell, etc) will freely attack floating eyes.

If you give your pet a scroll, and it is a scroll that monsters can normally read, it reads it on its next turn.

If you give an item-using pet an amulet of unchanging, they will recognize that you want them to wear it and put it on.

Chatting to a pet that is carrying an item picked up off the floor will command them to drop the item. The odds of them obeying depend on their tameness and apport.

In variants with shallow water, pet cats will avoid it similar to how they avoid squares containing cursed items.

If you are a Ranger, your pets will specifically seek out missiles you have thrown which are lying on the floor, pick them up (perhaps even collecting multiple ones at a time) and bring them back to your side.

A monster (imagined exclusively as a pet) that acts like your shadow in lit places, always being right next to you and possibly dying if it can’t be next to you, but if you’re in a dark area it is free to wander off.

Pets’ closeness to the player should correlate with higher tameness, so that if you’d prefer it stay a little farther away you can deliberately decrease its tameness or vice versa.

If you attempt to push a boulder onto a space where a pet is, it will automatically move out of the way if there is an available space to move to. If not, it stays there and the boulder can’t be pushed. This may or may not cost the pet a move.

You can tell shapechanger pets to change shape (but not what to turn into) via chatting to them.

If you are on a staircase/ladder (maybe a magic portal), your pets will always try to approach you (using the appr = 1 code path in dog_goal). Maybe, to make it a little less obvious have pets approach you (with a less than 100% chance) if you are merely near the stairs, with a diminishing chance of intervening to set appr = 1 the farther away you are.

Pets will never pick up large, bulky containers, like large boxes, chests and ice boxes. For one, picking up a heavy bulky object is unrealistic for many humanoid pets; for another, usually when pets pick up large containers they are doing something annoying like moving around a stash container.

A much more fleshed out interaction system for sapient monsters. It is initiated by chatting, which opens up a menu offering four key verbs: Ask, Tell, Show, and Give.

Ask is used to gain information from a monster; this could be a whole bunch of things, from rumors to identification to information about the dungeon. Each type of monster you can ask things of has a limited knowledge base, and this knowledge base may contain some inaccurate information. Especially interesting is the possibility that you can ask someone for identification, and they tell you what they think it is - which could be right or wrong, but a good clue either way. You can also ask someone to join you, and pay them some gold to tame them for a certain amount of time.

Tell is currently a less developed part of this idea; the only thing suggested so far is that you can tell a creature about traps you’ve discovered, which will make those traps known to the creature. You can also use “tell calm” on your pets to make them refrain from attacking peacefuls.

Show lets you select any item from your inventory to show to the monster. This can be used for intimidation (e.g. showing a stack of iron skull caps to a goblin).

Give lets you give items to a monster, which in some cases, depending on the AI, lets you test the effects of items.

Note that a potential pitfall of such a system is that if it’s complex enough to do interesting things with, it is probably going to be hard to use without spoilers. And if it’s uncomplex enough, it runs the risk of most possible responses being “I don’t know/care about that”, which also makes it hard to use without spoilers. A middle ground between these is likely to require an enormous amount of work.

If you die next to a pet that can make you arise from the grave, it infects you and makes you arise from the grave as that, without ending the game.

When you wield a treat in your hand, pets that normally like that treat will follow you even more closely than they would if you simply had it in open inventory.

A pet will only eat a corpse that will make it polymorph if its tameness is very low. Otherwise it will avoid it.

Demon and undead pets move reluctantly over blessed items.

Aggravate monster from a ring (and only from that) gives pets a special behavior: as they are aggravated, they will attack enemies with no regard to their current HP or the enemy’s level, basically ignoring the checks that exist. Enemies might also attack pets of their own volition (which they don’t do under normal circumstances except in retaliation).

You can command pets to come towards you, and also command them to stay in place until summoned.

Special message when a self-concealing pet “reluctantly hides under” a cursed item instead of stepping over it. Or maybe pets which hide under objects will never hide under cursed objects.

The ability to chat with intelligent pets and give them basic strategy directives, such as what type of attack they should be favoring, or whether they should stop attacking and stay by your side. Opinions vary as to whether this should be limited to intelligent pets or not.

When tame shapechangers polymorph, they attack creatures based on their current monster level (or perhaps the maximum of their current level and their new form’s level), not blindly use the new form’s level.

If you have autodig enabled and a digging-capable pet is next to a wall or rock square you move into, it will dig that square out for you.