Sometimes I see a 2D6 random table which includes a rule about doubles; usually if the two top faces are a double (i.e. the same number) then something unusual happens, e.g. a wildcard event.
What I don’t especially like about these ‘double’ rules is that these ‘doubles’ don’t feel independent of the main result. For example, ‘snake eyes’ or a double 6 are usually the worst and best result and always a double. So, you can’t get a ‘snake eyes’ without triggering the wildcard event. And maybe that’s OK.
… but, here’s a suggestion … roll the 2D6 (as normal) but also pinch the dice together so two faces kiss. Then look at the two faces that are opposite the kissing faces. If those opposite faces are a double, then trigger the wild card.
These ‘side doubles’ are more or less independent of the main result on the top faces, i.e. about 1 in 6* (although if the top faces are a double, then the probability rises (I believe) to 1 in 4, which seems app to my mind).
* For reference, in case it is not obvious, ignoring the side faces, getting a double on the top faces is 1 in 6.
‘Side double’ example:
If the below 2D6 are brought together (along the yellow arrows) such that the two faces are kissing. Then, the faces opposite the kissing faces are a ‘side double’, i.e. a ‘double 2’ (pink arrows). In this case it is just happenstance that the top faces are also a double (snake eyes).
This idea has its roots in this blog post: http://tarsostheorem.blogspot.com/2020/04/dice-are-statblocks.html
More on the maths
Please see: https://discourse.osrrpg.com/t/wrong-doubles-using-2d6-side-double/1136