The episode opened with Ted and Robin having typical roommate fights and trying to figure out how they were able to live together before without all the fighting. They quickly realize it was because they were having sex and jump back into bed together. They decide they're going to tell no one... and then Marshall enters the room. He scolds them for what they're doing warning someone is going to get hurt.
Thanks to Marshall, the whole group knows that Ted and Robin are sleeping together and it's killing poor Barney who's still in love with her. Everytime Ted makes reference to their hooking up (and he does a lot in the montage), Barney goes outside to the dumpster of McLaren's to break a television. When they run out of televisions, Barney goes to an electronics store and has an awesome, serious conversation with the employee about black levels and colors in picking out the best tv. Once he does, he takes it outside and breaks it. Classic.
Barney decided to head over to Ted's in order to clean his whole house to stop any potential roommate fights. Ted quickly sees through this (no bro cleans another bro's apartment) and calls him out on still liking Robin. Despite Barney still not coming clean (though coming very close several times and saying it's what Ted would say), Ted realizes that someone does get hurt when exes still sleep together... only it's Barney. Ted and Robin stop doing the nasty and all is good again.
Meanwhile, the hilarious side plot of the episode was Marshall who need to go home to "read a magazine" (aka taking a poop). He couldn't go at work because he though everyone was judging him. On the covers of the magazines he would read were all the celebrity guest stars of the episode (Heidi Montage, Spencer Pratt, Kim Kardashian and Kendra Wilkinson). By the end of the episode he eventually found the confidence he needed and we all found a new catch phrase for describing a number two.