Ted meets Blah Blah (real name Carol, but Ted can't remember it) while playing World of Warcraft but she ordered him to tell his friends they met in a cooking class instead. It didn't take long for Ted to figure out she was on the wrong end of the Hot Crazy Scale. Eventually Lily hears Blah Blah ended up at the psych ward at Bellevue.
Ted thought she was the perfect girl and was completely clueless as to why his friends hated her. But as soon as they told him, he couldn't drown out the sound. Cathy talked too much. He soon dumped her and when they met much later she's married to a man who's deaf.
Ted broke up with Natalie on her birthday. Twice! First over her answering machine with her friends listening as they gathered for her party. Then after winning her back, he realizes it's not going to work and he broke up with her again, this time in person. However it was unfortunate that he failed to remember it was her birthday once again.