Gonzo may not be the right word.
An example, a couple of sessions ago my nephew played with us, we rolled him up a cleric. After killing a bunch of priest we high tailed it out of the town.
A few months later we reconvene. My nephew wasn't able to make it to the session, and we were not entirely sure how often he was going to make it.
Obviously most DMs would just play the character in the background until such time as the player showed up.
Not us, our explanation.
While on the way out of town, the character slipped into a weird magical portal and was flung somewhere into an alternate reality, maybe he is with his god? who knows.
Next time he shows up, viola he will be in the right place at the right time.
This leads me to the idea of creating a house set of rules, we basically use basic fantasy, however there are a few minor tweaks that fit on one page:
Attacking: Add your d20 roll + attack bonus + STR/INT Bonus + Magical Item Bonus (where possible)
Damage: Weapon damage + STR/INT Bonus + Magical Item Bonus (where possible)
Ability Checks: Ability checks are based on your level, at level one you need to roll over 17 to succeed, Level 2 - over 16, etc. Ability checks are called for by the GM, or when a player wants to do something that isn’t covered within the rules. Ex “breaking down a door = strength check”. A modifier may be made to the roll in certain circumstances.
Double Damage/Crits: When attacking if you roll a natural 20, you can roll 2 damage dice instead of one. All bonuses are only added to the first damage dice. If you roll a 1, your weapon breaks, you drop it, or something equally embarrassing happens.
Thief Sneak attack: a sneak attack is made with a +4 attack bonus and does double damage.
Saving Throws: When you need to make a saving throw, in order to be successful you need to roll over your given number. Ex a fighter making a death saving throw must roll over 12. In most cases a saving throw vs death/poison will be made. Add Racial Bonus to roll. Dwarves + 3, Elves + 2, Halfling +3, Humans + 0. Note: We only use one saving throw, which is VS spell.
Thief Skills: Roll under appropriate ability with percentile dice.
Cleric Turning Undead = Table Page 50
Inspiration: The GM may give a player inspiration because they are role playing their character well. When you have inspiration you can choose to reroll any dice, whether an attack roll, ability check, or saving throw. Once inspiration is used it is gone, until you earn it again.
Death & Dying: If your character’s hit points become 0 you are considered unconscious. If your player’s hit points become negative numbers you need to make death saving throws. If you roll under your death saving throw number 3 times you die. If you succeed twice in 3 times you become stable. 0 hit points.
Experience and leveling up: After 2nd level you will need to find an appropriate trainer to help you level up, regardless of experience totals. For level 3 it will be 300 GPs. For level 4, 600 GPs, and so on. Obviously your hit points, attack bonus and saving throws get better when you level up.
Rest: PC’s regain 2 hit points from a good night's rest. Recovering from major wounds will take atleast a week or more. Spent spells are regained the next morning.
Another silly example was when a thief went off to get trained. He found a trainer and started sailing the high seas after a session. We reconvened very quickly, like maybe a week in between. I decided the thief was on the ship, and the water became really rough, he fell overboard, and another wonderful magical hole appeared, he then landed confused infront of everyone.
I had a discussion with a few of my players about Swords & Wizardry light, they all thought it was a pretty cool concept, however they do like having variable weapon damage, and more than 2 dice. Personally though I think the next time I run a campaign, I may just switch to it, with some added house rules. (Inspiration & Dying from fifth). Our sessions have really become less crunchy fighting, and more role playing. The basics of S&W light work well for the way we like to play. So that is probably going to be the essential plan at some point.
The other thing I was thinking was creating a few more random tables that would go with the whole concept of it being rather silly most of the time. As an example having a table that explains why a PC is missing, and how they show up again, would be relatively handy.
I really love playing old school games, because of the infinite hack-ability.