This page covers evidence indicating a coupling of Theodore Seville and Eleanor Miller.
Evidence from Alvin and the Chipmunks (TV series)
The Gang's All Here
Soccer to Me
Big Dreams
In one future timeline, Theodore and Eleanor are married and open a restaurant/nightclub.
Evidence from The Chipmunks (TV series)
Evidence from The Chipmunks Go to the Movies
Evidence outside the series itself
I Love the Chipmunks Valentine
Eleanor makes Theodore a cake, and Theodore makes Eleanor cookies. Both Theodore and Eleanor share a dance.
The Chipmunk Adventure
Eleanor kisses a Theodore doll.
Alvin and the Chipmunks Meet the Wolfman
When the Book of Monsters arrives in the mail for Alvin, it came with a necklace. Alvin finds it and threw it out the window which led to Theodore finding it and giving it to Eleanor.