During his run on "Billy", Galecki began making guest appearances on the hit ABC sitcom "Roseanne" as the younger brother of Mark Healy (Glenn Quinn), who began a relationship with Darlene Conner (Sara Gilbert). Introduced in his first appearance as Kevin Healy, his name was soon changed to David. After a few more guest shots, Galecki was named a permanent "Roseanne" cast member from the fall of 1992 onward, after the cancellation of "Billy". He would remain in the role of David Healy until the end of "Roseanne"'s run in 1997, with the character eventually marrying Darlene and fathering two children with her. Galecki's character on "The Big Bang Theory" would also have a short-lived relationship with Gilbert's character on the same show.