I’ll post another photo once this opens, but I have a new mystery. This plant was labelled Odyssey, which it obviously isn’t. My Odyssey tubers came from my own stock, and I don’t recall growing anything with this color scheme last year. Also, this is a new area in my dahlia garden, so it’s unlikely that this was a deeply buried tuber from years past that has a strong will to survive. I guess my dad might have given me a tuber that was mislabelled and I planted it here and I don’t remember? Or maybe I was sent a NOID tuber with a purchase and I threw it in here and forgot? Anyway. Surprise!
ID help?
Juliarugula total speculation... AC Rosebud
I grew it for the first time this year and the colors look very similar.
Bessie you’re right - it does look similar. It’s not one I’ve ever had but like I said, could be a NOID.
Identifying unknowns can be frustrating to both the person asking and the person being asked. The person asking should have labeled it says the person being asked. Then throw it away as it has no value. The person asking says it has sentimental value. All the more reason you should put a label on it. But I did not and what is this one? There are at least 5000 dahlia varieties being grown and my computer brain does not have a picture of each one in there. You should have put a label on it . They never say go ahead and invent a name for it and why not as they are not going to sell it.
Teddahlia You should have put a label on it
But I put a label on it. It said “Odyssey”. 
. (Odyssey is actually growing beside it).
I have remembered that last year I tried to grow AC Outlander in a nearby spot but ended up pulling the plant as it seemed pretty sad. I wonder if this is a leftover tuber from that plant. This was a new patch of ground in my dahlia garden but I probably moved some shovels full of dirt around while digging.
For me, I think the curiosity is more that I have random plants from years previous pop up, and I sort of kick myself that I sometimes can’t figure out what they are. Tubers aren’t supposed to overwinter in ground at all in our area, but every year I have surprise return visits. This year Zwink, Rhadeghast, and Canoz Jaguar returned. And maybe this guy?
Last year I had one return from at least two years prior which was crazy to me. It’s back again this year. I tried (not super hard) to dig it out last year, but it’s really deep and I didn’t care enough.
Once in a while I have an unknown variety come up in a row of "known" varieties. So far, it has been a seedling that had germinated from last years seed pods that I left on the plants. Usually, the poor form will reveal the deception but sometimes the form is pretty good and one year I tagged one to save for a second year.
Part of problem is that the average person on the street thinks a long time dahlia aficionado should know all the varieties as there "cannot be more than 100 or so." The dahlia expert has been through the dahlia identification a thousand times usually without much success and is rather tired of everybody not using a cheap little tag to record the identity of the flower(s). I have been telling people how easy it is to search by picture on Google but that seems to be more technology than they can handle. 
Hapet Pearl, shown by Teresa Bergman to Best MB in show.
Juliarugula forgot? Anyway. Surprise!
Figured it out! It’s Bubbling Over, which was grown nearby last year. I must have moved a volunteer tuber around in a shovel full of dirt when I was prepping beds.
19 days later
Juliarugula Returning to your mystery bloom, I am glad I took a closer look at what I have still blooming here yesterday. I put a Camano Zoe next to Odyssey, which was beaten down by spider mites or something awful early in the scalding heat of June and July. I saw this pretty pale pink one and just assumed it was C. Zoe, but on closer inspection, it is Odyssey! The plant survived after I chopped it down to nothing months ago. Here are some pics, with HH Miss White for comparison too.
I feel like Odyssey is what I hoped C. Zoe would be. @Teddahlia is right. C. Zoe has an ugly center at both ends of the season, and a very short window during which it looks good. I also like the one that you posted above. I was doubting if I’d keep Odyssey, since it succumbed to disease or pests. But I think it might replace C. Zoe, which has frustrated me for a few seasons.
Juliarugula
I think Pink Pearl but may later resemble wizard of Oz
Juliarugula
Nadia Ruth? maybe
21 days later
Juliarugula Odyssey is one of my favorites 
but I now write the variety, seller & price paid on a tree tag & wrap it around the tuber when I plant & that has solved lots of mysteries when I dig them up 