Had a fun session over the weekend, and had to share it. As a DM, have you ever had your players come up with a plan so awesome in its ridiculousness that you just had to let it happen, even if you had to change things to get there? This was us yesterday.
Spoiler: Path to the plan

The setup was that they were out to deal with a coven of sea hags. They had to "deal with" them, which leaves a lot of opportunities. The hags lair was in a cave off of a river. The initial cave was where they had a knight standing guard as part of a deal they had made. Someone comes along looking to deal, the knight gets some basic information, goes through some underwater tunnels to get to the hags, discusses, and comes back. If the hags want to deal, the knight gives the person a potion of waterbreathing and directions to enter the actual lair. The hags were more powerful than the adventurers as a coven, so this was as much to keep them from rolling in and getting wiped out as anything.

The parties bard ran off ahead of the rest of the group, looking to create a diplomatic solution. She was able to strike a deal where the hags would not accept anyone from the city that was concerned about them, in exchange for the bard writing a song about them and singing it across the continent. This song would have been an incredible boon to the hags - basically advertising, allowing them to amass more power and raise their standing. They absolutely lowballed what they would trade for the song - had they really negotiated, the hags would have completely uprooted themselves and moved a thousand miles in exchange for the song. But the bard suggested the deal, they went along with it, and she asked them for something to write about.

Meanwhile, the rest of the players ended up fighting the knight, and winning. They subdued him, and had him bound up for interrogation. The hags added that they wanted their knight back, and sent the bard back to deal with them. They discussed, and eventually we stopped the session because the paladin's player wasn't there and we felt he needed to be part of this. Next session (last Saturday), everyone was there, and they started to discuss things. For an hour. The bard was saying how the hags hadn't hurt anyone, the wizard was on her side mostly from a 'who are we to interfere with consenting adults selling services' standpoint. The paladin was communing with his god. The blood hunter wanted to waterboard the guy ("he's tied up and there is a deep pool of water right there"), while the hobgoblin artificer thought that some beings were just inherently evil and they had to wipe the hags out. The paladin ended up wanting more information to decide whether they needed justice or mercy, two pillars of his faith. Eventually, they decided to interrogate the knight.

They got the knight's story, and it had enough of them worried that they slowed down on any dealings. His story was that his newborn twin daughters were taken from him on the day of their birth. He had been trying to find out what happened to then ever since - they would have been 13 a few months back. Almost a year ago, he had found the hag that leads the coven, and asked for help finding his daughters. She offered a deal that if he protected her for a year and a day, she would tell him where to find his daughters. He agreed, and the time is soon to be up. The players all had a little bit dawn on them that the other two members of the coven were the daughters at issue. So now they argued about whether that was actually true, whether anything could be done, and whether they had the right to police the world. Eventually, they got the knight to agree to go to the hags and ask if they would come out and talk.

The hags would not, but they gave a note with what they wanted to have in the song. It told of the knight, and confirmed the thought on the daughters. It also told of a woman who came to them because she was barren and her husband, a young knight, desperately wanted children. The hag agreed to make her fertile and able to have many children, if the hag got the first issuance from her womb. She agreed, and took the twin daughters as payment. Then it went a step farther back, how a nobleman was worried about siring children with all the peasant women he was dallying with. She made a deal with him to send troops to eliminate a monster (which was a more powerful hag), and assured him he would not father any children. She did this with a curse that he would make any woman he slept with barren. Well, the players quickly put the pieces together, and diplomacy was out the window.

The players now wanted to get into the back chamber by any means necessary. I hadn't really mapped that out, I just knew it took a bit of time swimming to get there. But they started in on a plan, and I quickly warped geography so this would work. The bugbear blood hunter's player recounted how if they had some vinegar, they could do what Hannibal did crossing the alps to widen narrow passages - heat the rocks with fire, quench it with vinegar, then it should be cracked and easy to remove. The artificer had received a jug of alchemy recently, and he heard this and got a huge grin. They explain to the knight what the deal was, and after stopping him from killing himself, they got him on their side. He said the hag's chamber was just on the other side of the cave wall, and they could conceivably make it through. One of the players queued up the A-Team theme song, and they discussed how they would do this. Eventually, they had a flaming sphere pressed against the rock to heat the wall, the vinegar from the jug ready to be poured on, pitons attached to a chain, attached to a block and tackle that was anchored by an immovable rod, with the team of horses ready to pull. I was so entertained by this whole thing that of course it worked! The wall came tumbling down, and they started flinging spells back and forth through the gap in the wall. Eventually, the hags fled, but not before the wizard mind spiked the leader. We had a whole chase scene, they caught her, but her daughters split up. We'll resolve that next time.

It was such cool teamwork - everyone had a part they had to play and found creative uses for what they had. I had to honor the bugbear's player by creating a story about the legendary bugbear general, Hannab Al'Barca, and his attack with mammoths. The character is now a direct descendant of the general.