Happy Days (theme song) by Artist Unknown Sunday, Monday, Happy Days. Tuesday, Wednesday, Happy Days. Thursday, Friday, Happy Days. The weekend comes, My cycle hums, Ready to race to you. These days are all, Happy and Free. (Those Happy Days ) These days are all, Share them with me. (oh baby) Goodbye grey sky, hello blue. There's nothing can hold me when I hold you. Feels so right, it can't be wrong. Rockin' and rollin' all week long. Sunday, Monday, Happy Days. Tuesday, Wednesday, Happy Days. Thursday, Friday, Happy Days. Saturday, What a day, Groovin' all week with you. These days are all, Share them with me. (Those Happy Days) These days are all, Happy and Free. (oh baby) These Happy Days are your's and mine. These Happy Days are your's and mine, Happy Days. Oh yeah, that's what I'm talking about.