Happy Sunday is a Korean reality-variety show shown on the KBS2 network, which competes directly against MBC's Sunday Sunday Night and SBS's Good Sunday line-up. Although it has been broadcast since 2003, its line-up of shows has frequently changed, with a complete revamp occurring in Spring of 2007. At that time, three new shows were introduced – Are You Ready, High-Five, and Immortal Music Classics. Due to its poor reception, Are You Ready quickly evolved into 1 Night 2 Days, with most of its cast intact. In late November 2008, Happy Sunday had a revamp of its shows keeping 1 Night 2 Days as the second segment and bringing back Immortal Music Classics which was previously liked by viewers. However in late March, Immortal Music Classics ended once again and was replaced with Qualifications of Men, making Happy Sunday an all-male cast, with a total of 14 members. In 2013, Qualifications of Men was cancelled and replaced with Star Family Show Mamma Mia.

Out of the three Sunday night shows, KBS's Happy Sunday, MBC's Sunday Sunday Night and SBS's Good Sunday, only KBS has kept its program as a "whole program." Both MBC and SBS has divided their Sunday night show into two parts, the first segment as one program and the second as another. Both MBC and SBS have done this to record better TV ratings, which is important in South Korea media to prove the show's popularity. The key variety programs which garner Sunday night ratings and are usually compared to one another are Happy Sunday's 1 Night 2 Days, Sunday Sunday Night's We Got Married, and Good Sunday's Family Outing.