Jenner Separation -- Happy Kris, Sad Bruce

The Jenner split has become a tragicomedy ... Bruce can't seem to muster a happy face, and Kris can't help but smile.

The separated duo both showed up to a production office in L.A. today, wearing drastically different expressions -- just one day after announcing they were living apart.

Both have said they're happy with the current arrangement, but Bruce was cursing like a sailor yesterday about it ... and appears to be clinging to his wedding ring. Unlike Kris.

Still, gotta respect their work ethic.