Many Happy Returns was a Supergirl storyline from issues #75 to #80 in the 4th Supergirl volume, and the final story within it as well. It focused on Kara Zor-El somehow appearing in the post-Crisis reality of New Earth and her adventures with Linda Danvers before ultimately being forced to die in he old reality in Crisis on Infinite Earths.
The primary antagonists for the arc were original creations, Xenon, Fatalist, and Rebel II, though minor villains such as Mister Mxyzptlk appeared as well. Supporting characters included Superman, Superboy, The Spectre, Cutter Sharp, Fred Danvers, and Sylvia Danvers.
The story serves as a final story for Kara, but was not her first appearance in the post-crisis reality, as she previously appeared as a ghost in the Deadman story, "Should Auld Acquaintance Be Forgot?", appearing in Christmas Time with the Super-Heroes #2.