Quote from Marshall in Of Course
Marshall: She was obviously crushed. Ted: Wait, but that would mean... Oh, no. Future Ted: [v.o.] And then I realized what a jackass I'd been to Robin. [flashback to Ted joining Marshall as they discussed Barney's sex life at MacLaren's:] Marshall: I said a bang, bang, bangity bang Ted: Hey, what you singing? Marshall: Just a little ditty I wrote about how many girls Barney's been banging lately. Ted: Well, count me in for a verse. Marshall: Great! Both: [singing] Bang, bang, bangity bang I said, a bang, bang, bangity bang Bang, bang, bang Bang, bang, bangity bang I said a bang bang...