How to do a "Game within a Game" mini adventure?

My current D&D 5E game is rather whimsical by design, and as part of a future adventure I really want to try and do a Game within a Game scenario. And specifically, I want them to play an old school basic D&D game with their current characters as the players. I'm talking original D&D - well, Rules Cyclopedia, to be specific, but still. My thoughts were that this would require new character sheets, but I'm not sure how to implement that when our game is already bound to the OGL 5E sheet. I'm looking for tips on how to do this without starting a whole new campaign just for this one-shot. I want the players to have their actual characters' skills and stats, as well as the new ones in the older game system. I'm still new-ish to the tools available here, and looking for advice on how to most easily implement this. Thanks!

The easiest way is to create a new game for your game within game and supply an invite link to your players. This will allow you to run the game with the sheets you want but you will have to build the OD&D characters all new more than likely. After your game in game is over, just have everyone move back to the original game and continue. There are lots of advantages to this as it will allow you to continue the game within game aspect if it comes up again without worrying about it disrupting your original game and other aspects.

There are other approaches to this, depending on what's most important to you in your setup. How important is the D&D (basic) Character Sheet, compared to the importance of maintaining your 5E Characters skills-and-stats including their macros or sheet-rolls if you use a lot of macros or sheet rolls? We cannot use 2 different Character Sheets at once in a single game -- though there is a Suggestion for that on the Suggestions forum. We can use the BIO TAB as an excellent place to write a text-based "Character Sheet" (you could put the format of a D&D Basic character here on the Bio Tab), this would allow you to continue using the 5E Character Sheet on the actual Character Sheet tab, in order to preserve all those macros, sheet roles.  Since back-in-the-day players used to regularly write-out a character on a piece of lined notebook paper, or type up a character, this can be simulated by using the Bio Tab for the new Basic character.  As DM you can provide them with a format for the plain text Bio Tab, such as Name:____ Class:____ Strength:___ etc. You can also add Attributes on the Attributes & Abilities Tab.  As long as you give new attributes a unique new name, it won't disrupt your existing 5E Attributes.  For example you can add on each Character, new attributes perhaps named such as Basic_Strength, Basic_Class, Basic_HP, Basic_AC .  In this way you and players can actually set up new macros and rolls that leverage the actual Basic D&D scores, but it just wouldn't show on the Character Sheet tab and wouldn't have a nice character-sheet-looking-format. It would just be a series of scores, values, called Attributes. Back before Roll20 introduced the Character Sheets technology, players here used to actually mark-up the entire character using just the Attributes tab.  The Character Sheet tab is actually just a fancy formatting of the Attributes.  Click over to the Attributes tab of your existing 5E characters and you'll see what I mean. In short, I'm suggesting it might be easier to toss the relatively-small amount of Basic D&D stats onto your existing Characters by using the Bio and/or the Attributes, whereas it would be probably harder to start a new game with the D&D sheet and still be able to let "players to have their actual characters' skills and stats" from 5E OGL.  However I also agree with Pat that starting a new game for your side-game-within-a-game is a valid alternative, depending on which set of stats is more important for you to use on your one-choice actual Char Sheet tab.

Thanks for the tips, folks!

N. Phillip Cole said: I want them to play an old school basic D&D game with their current characters as the players.  The concept is wonderful. So you're going to have your 5E Characters find, for example, a table in a room and the table has miniatures and some mysterious books on it?  And the characters sit down and read the books and start to play a game, which turns out to be them playing D&D within D&D?

Actually, a bit more involved than that. The PCs are all students at Adventure School. It's the kind of game where the characters are all very directly aware of concepts like Hit Points, Armor Class, and Experience Levels. They will soon be taking a class called "History Appreciation" or something like that. The class will send them on an adventure as a team of roughly equivalent OD&D characters (as best as we can, since we have a Kenku and a Yuan Ti in the group), only with the roles swapped around. So the Players will be playing their characters, who will in turn be playing different characters, in a fully realistic simulation.