Ted and Barney both decide they want Robin back as she and Don get serious.
Don has issues with the fact that both of them dated Robin, but he warms to it.
Ted and Barney warm to him too ... but they're both pretty jealous of him, really.
The two proceed to get sloshed and debate the reasons they broke up with her.
Then they decide to get back together with her anyway, by any means necessary.
Robin eventually moves in with Don, taking a break from the crew for awhile.
Marshall and Lily invest in some twin beds because it helps them sleep better.
It's not the best thing for their marriage, however, although it was amusing.