for some reason I am reminded of a thing I came up with when visiting my friend a few months ago. Bear in mind I have made no effort whatsoever to flesh this out, it's just a nebulous concept at the moment, but all the same:
if you and your group dont want to commit to a long and drawn out campaign, you could try something like this: everyone puts an idea for a random encounter on a bit of paper, along with a kind of dice, and a number appropriate for it. This includes loot finds, monsers, etc, and also character templates. The idea is to do a mad-libs kind of random one-off session. Absurd actions, loot items, and outcomes are ENCOURAGED. we are talking things like "Traveling Drow televangelist" and "gnomish interior decorator" level of absurd here. once you have all the batshit crazy from your players collected and organized in your notebook, you load up a bingo tumbler with as many whole bags of dice as will reliably fit inside.
Now, rules are fast and loose. no rule lawyering, since this is meant to be pure silly. To start, each player rolls the tumbler to determine what they are playing as (die value and type together determine, based on what the players threw down earlier.) Once everyone knows what they are playing as, the DM tumbles and collects a die from the tumbler to state the current objective. (again, the type and value determine). then rolls again for the first encounter.
each player gets a turn, each drawing a random die from the tumbler. Regardless of how absurd the drawn die, that is what determines how effective your chosen action was. at the monster's turn, a die is selected which determines its action and outcome. When the players vanquish the monster or finish the encounter, a draw from the tumbler is made for loot. this continues until either everyone dies spectacularly, or the tumbler runs dry.
This kind of thing is intended for "everyone but a few people cant make it this week" type nights, where you want some fun, but dont want to progress a campain.
I am sure there are problems with the idea, it's just a nebulous concept after all.