Quote from Ted in Twin Beds
Don: Hey, Ted, do you think it's weird that Robin is still friends with Barney?
Ted: I think it's weird that we're all still friends with Barney.
Don: I just don't know how I feel about her hanging out with one of her exes all the time.
Future Ted: [v.o.] And that's when I realized Robin had failed to tell Don about another one of her exes, me.
Ted: No, hanging out with one ex is fine. Even two, I'd give a pass. Hell, two might be even better than one, for some reason.