Just curious how you guys would rule a spellcaster using his familiar to administer a potion to an unconscious ally.
I didn't want to interrupt play and fell back on the rule of cool in adjudicating the action, but it was an AL game so I'm looking for a by-the-books response. This was how I ran it:
The rogue got pushed out a second story window and took falling damage sufficient to reduce him to 0 HP. The wizard saw this happen, but there were enemies between himself and the window. He gave his weasel familiar a healing potion, and instructions to feed it to the rogue. I ruled that giving the weasel the potion was a free Interact with Object, and the weasel could move to the rogue on his own initiative count, but the wizard would have to use his Action to see through its senses in such a way that he could instruct it to administer the potion.
As long as the familiar has the physical capability to properly manipulate the potion bottle and remove the stopper/cap, I see no reason to prevent the familiar from being able to use its action to administer a potion to an unconscious creature.
The find familiar spell specifically states "A familiar can't attack, but it can take other actions as normal." so it is entirely supported by the rules text to allow a familiar to do anything which the animal it is in the form of is capable of that isn't an attack of some kind.
Looking at the standard list of familiars, most are likely incapable of opening and administering a potion (frog and fish, certainly), some could probably manage it but I'd expect some difficulty in their doing it (cat, for example), though I'm not sure if that difficult is worth modeling as taking more effort than an action, and a few are absolutely capable and would likely find no challenge in the task at all (octopus and weasel, both having the appropriate appendages to make easy work of it, and the puzzle solving aptitude to not have to be specifically trained to do it).
Nevvur wrote:
"...the familiar has the statistics of the chosen form..." which includes intelligence. Unlike Find Steed, this is not an exceptionally bright version of the animal, spirit or not. This was the line I recalled during the session which prompted me to require more active control by the wizard.
Got me thinking though, would you allow the familiar to take things with it into the pocket dimension when it is dismissed, and reappear with them later? Nothing in the text about it, so I suppose it's DM's call. Could make for some fun familiar shenanigans... Bandolier of healing potions to be the party's combat medic... a method of smuggling small items with zero chance of detection...
This is something I'd definitely do with a chain warlock, using an imp or sprite familiar, since they're intelligent and anatomically capable of administering potions. I'd give him an itty bitty belt of potions, and standing instructions to administer a potion anytime one of my allies fell in combat. Even if the DM didn't allow for carried/worn items into the pocket dimension, he can just remain invisible most of the time.
Thats a very cool idea. I am sure the warlock in my group will be ording a custom bandoleer for his Sprite soon to slot in 2-3 healing vials.. 
Personally I would encourage the player to make use of their weasel familiar as a carrier of said potion - perhaps with a harness - or perhaps rolling/pushing the potion along a flat surface for a short distance.
As for administering the potion? It would depend on the potion's container. A cork/stopper/cap may be too much for a weasel to manipulate in a timely manner, though with a little wiggly-room we might claim that weasel uses their teeth to unbung/flip/open the potion's container. The challenge of manipulating the container into place though? Tricky and certainly not something done at any pace.
Now, if the rogue was stable and the mood/game was suitable, I'd be happy to have the little furball lick the rogues face, allowing them to briefly regain consciousness and drink said potion - perhaps with a Con check.
But hey, we're dealing with a fey creature that happens to resemble/have the form of weasel. Perhaps they have Disney-style anthropomorphic limbs/hands? Really though, the important thing is consistency - if you're happy with your arbitration of the event and are happy to set a precedence for friend and foe alike to do the same, then it's all good!