I think this is the song you're looking for; my best friend always sang this song, and I learned it from him in the 60's. It had to be by a country western star, and I've been trying to find the actual lyrics and artist too, to no avail. Here's they lyrics as I remember them and sang to my kids for the past 30 years, I rememberd every lyric, except last ones that captain Packrat provided! I still would like to hear a version of the original some day.

Oh The radio said that you better look out, cause here come the little green men,
And if they land in your back yard then you better not let'm in.

Well I just ignored my radio and stepped out on the lawn,
And there was a couple of little green men, they were doin it arm in arm.
Sing'in, hi dilidilum... hi dilidilum... hi dilidilum... hi dilidilum-lum.

Well I watched them for an hour or two and then they discoverd me,
And one of the men said double-eck, double-oh and double-oh, figero Gee,
Which means take me to your leader boy I'll tell you any thing,
You see up on the moon where we dont have jive, so we come down to earth to swing.

And through every US radio station, the little green men spoke to our nation, then we caught a translation of the funny little tune,
Saying, "See ya' later, alligator. Plant ya' now and dig ya' later." Up went the itty-bitty escalator and they flew back to the moon.