20 Shows With "Breakout" characters (characters who were originally intended to be minor ones who became the most popular ones on the show... include the name of the character, of course.
1. Happy Days - Fonzie. Yes, as iconic as he became he WAS originally intended to be very peripheral.
2. Grey's Anatomy - Addison. Since she was only to guest on 3 shows, and shes getting her own spin off after 2 seasons.. I'd say shes made an impact.
3. Cheers - Frasier Crane (IMO)
4. Night Court - Bull Shannon
5. Family Matters - Urkel (even if ya' hate him, you have to admit he became the main focus for the show... given that he was originally just the "pesky neighbor" character, he definitely fits our criteria)
6. Soap - Benson, he did get his own show after all
7. Star Trek - Spock (originally he was just part of the ensemble--not the co-lead he pretty much eventually became...)