After the news of The Great Pumpkin Shortage and the one-month anniversary of Steve Irwin’s passing, you may need an excuse to laugh. We gots one. Washington Improv Theatre has two nights-worth of back-to-back improv comedy at the Mead Theatre Lab at Flashpoint. Tonight’s 8 p.m. show includes two performances, one by the Daily Grind. Think Office Space on stage. In case you didn’t get enough Janet in HR at work today, Daily Grind will…