David, I have used it as a pollen parent. The cross is Carefree Beauty X Mutabilis. It is registered as Chireno and is being offered by Chamblees roses in Tyler. You can take a look at it at Chamblees web catalog or my listing on HelpMeFind. Chireno also sets hips and I have obtained one or two OP seedlings last year, and hope to have it be receptive to pollen this year. I have been unable to have sucess with pollen on Mutabilis but will continue to try, as it is a great rose. Ray Ponton
Jim, did your Plaisanterie seeds germinate? I’m thinking of buying it, but would like to know how it worked for you as a seed parent.
Rob
Weeks has a 2008 Mutabilis-type introduction coming out called ‘Watercolors’. The flowers look good. It’s (Santa Claus x Flower Carpet) x Betty Boop
Tom is doing some innovative stuff. I’m glad. I hope it sells.
Searching Happy Chappy, this thread came up. I saw the plant first hand recently, and, ironically, remembering that someone had asked I was thinking, “Now that might be interesting to cross with Mutabilis.” I did not recall that you had already posted that thought here in this thread, David, but would like to put in my vote.
HC starts out with sulfurous overtones deepening towards cerise much like Mutabilis. It is a ground cover rose, and likely has some interesting species genes in it, though listed simply as seedling x seedling. It sets hips quite readily from what I see, has compact growth, and might counter some of mutabilis’ poorer traits.
I wouldn’t expect the next big thing to come from such a cross, but as a diversion, I think it could be a fun one…
Bengale Sanguine blew as a seed parent for me. Like 20 tries this spring, and they all fell off. Oh well… at trying to see if it mixes with yellow very well…
Rob, I just saw your question about Plaisanterie. It sets hips well with diploid pollen. I don’t know how they germinate. I lost all of my seeds last year, over 3800 of them, to a fungus. I’m trying again this year. You have to be an optimist to be a rose hybridizer.
You really do, lol. Or annoyingly persistent 
Thanks Jim, maybe I’ll get Plaisanterie next year. Sorry to hear about your lost seeds. 3800!!