When is St.George's Birthday?

When and where did adding cha-cha-cha to the Happy Birthday song begin?

• My sister is a school teacher in Pennsylvania and we recently attended a nephew's birthday party in Maryland. All the kids at the party added "cha cha cha" to the birthday song when the cake came out. (As in, "Happy birthday to you, cha-cha-cha, Happy birthday to you, cha-cha-cha, Happy birthday dear _kids name_, Happy birthday to you, cha-cha-cha!") ... My sister was surprised because she thought it was just something kids in her school did to be weird. After asking around the party we found that parents from other states say their kids do it, too. We want to know where it started, when it started, who started, etc. (Also, apparently there are alternate additions besides the cha-cha-cha, too, but I can't remember them.)

• Answer:

  First commercial version is by Bob Azzam performing "Happy birthday cha cha cha" (trad./arrgt. B. Azzam) at the beginning of the 60's. Long missing from the market, it can be found now on "Bob Azzam & Son Orchestre - En France"