Kermit the frog caused 9/11. In the 2002 TV film "It's a Very Merry Muppet Christmas Movie", there's a part where an angel shows Kermit an alternate reality where he was never born. For whatever reason, the editors didn't really think about it, and continued to use footage with the twin towers still standing for this scene, however they aren't there in his original universe. Therefore, something that Kermit did in his life, did in fact cause 9/11 in Muppet lore.
Frog stack build: grung beastmaster, giant frog companion, magic innitiate feat for find familiar. Then cast animal friendship on a giant toad. Put your familiar (frog of course) on your head, mount your giant frog, have that frog climb onto the giant toad. Regular frog uses help action on you, you do player things, giant frog does help action and tether attacks as necessary, and the giant toad attacks and moves. I don't care how viable this build actually is, it is the only good build in the game.
Was curious if attacking while inside the frog should be a normal attack since I can't be seen by the frog. I doubt this is as intended, but curious what others' thoughts are.
Edit: looking at comments I think I'm going to make this situational based on how my players describe their actions and what those actions are. Larger weapons that do slashing or bludgeoning and require more of a range of motion to use, will likely get disadvantage. Piercing weapons really only need to be driven forward a bit so could be a normal attack (smaller slashing weapons may be fine as well). If a ranger has xbow expert and extra attack, the xbow would already be assumed to be loaded so the first attack would be normal, the fumbling of trying to load a second arrow and fire it off would be at disadvantage. If spells require a component and is in a component pouch, disadvantage, but if they are using a focus already in hand or if the spell doesn't require material components, sure, make it normal, but if the spell requires sight it won't be possible.
Edit: Someone else mentioned giving disadvantage on the damage roll instead of the attack, as the ability to swing a weapon hard would likely make the damage lower. I think I like this for melee attacks. Not sure about spells though, depending on the spell. Thunderwave may result in exploding the frog outright, but possibly deafening the player inside for quite a while.
My kid wanted me to post this. I didn't know where to put it, so here it is. Please be kind.
I told him the joke about a chicken that goes into a library and say "bwock!", so the librarian gives it a book and the chicken walks out. The next day, the same thing happens. On the third day, the chicken says "bwock bwock bwock!" so the librarian gives it three books. Curious, the librarian follows the chicken into a swamp where it puts the chicken puts the books down in front of a frog who says "reddit reddit reddit".