Creating special characters in AutoCAD can make you feel like you are in a secret club that knows all the codes like %%D for diameter and %%P for plus or minus.
The Mtext dialog has some real strange symbols hiding under the @ button like Monument line and Not equal. Squared and cubed are included but what if you get into a situation like 1st where you want super script the letters st?
There is a little trick with the stacking function that can really be useful.
In the Mtext dialog add the ^ symbol found above the number 6 on your keyboard ahead of text that you want to be a sub script. Select the text and the ^ then click the stack button and boom, there you go.
Do the same for a super script but in this case put the ^ after the required text.