I have a 60W MagSafe charger (2012 Macbook Pro) and am wondering if the extension cord is removable so that I can just plug the actual "brick" into the wall with a fitted adapter? It doesn't seem like it's removable, so don't want to apply too much force - but would be neat if it is!
Yes. All Apple MagSafe adapters have universal / interchangeable connectors where you can use your preferred length and polarity and groundedness connecter of regional preference to mains power.
The internal connector is standard IEC C5 or C7, and Apple adapters connect to the metal earthing pin optionally based on the cord or adapter chosen. Get a good photo of the gap, since a drop or crush can make the part very tight to remove. The removal is quite linear with not a lot of play so hopefully you don’t have to break things to get it apart.