When you have to keep all the characters in a show together, sometimes you have to get creative. List a few examples:

That ‘70s Show - When it was time for Eric and Donna to move to Madison for college, Red has a heart attack (caused by Fez and Laurie‘s marriage of convenience), forcing Eric to stay home with his family. Donna stays to be with Eric.

Boy Meets World - After Cory and the gang graduate high school and move into dorms, Mr. Feeny stays with them by becoming a student at college, and then, (within one episode) works his way up to teacher (or professor, whatever he’s called).

I Love Lucy - When the Ricardos move to the country, they have to leave the Mertzes. However, Fred and Ethel move to the country to go into business with Lucy and Ricky, raising chickens.

Full House - Instead of Uncle Jesse moving out with his new bride, the newlyweds move into the Tanner's attic. Thus keeping Uncle Jesse on the show and in the family.

Hmmm... I can only come up with one right now. I hope it's good enough.

When they fired Lisa Bonet from "The Cosby show", they had her character Denise go abroad with her husband. But in order to still keep a very young Raven on the show, they had her character, Denise's stepdaughter Olivia, live with her stepmother's parents instead of with her mother or any of her real grandparents!

Laverne & Shirley when the girls decide to move to California the whole gang joins them.

The Suite Life Of Zack and Cody-They're moving from the hotel to a cruiseliner. A new setting with most of the cast going along with them.