This doesn't happen in Mount Pleasant, but luckily for us, it's only about four blocks away. Sticky Fingers (Columbia Heights) had a cupcake happy hour yesterday from 6pm-8pm.
As a matter of fact, it will happen every first Wednesday of the month at that time. Cupcakes will be $2 each, down from the various other higher prices you normally pay. Wednesday is always a tough day at work, so might as well treat yourself. Or myself. See ya there in JAN. 1345 Park Rd NW, four blocks from Lamont Park.