Two of these showed up this spring in different parts of the yard. Any ideas? Thanks very much!

Interesting plant!
I haven't found anything to confirm her ID, but it looks just like this one shown in the below link, listed as a Mimulus (Monkeyflower) species:
http://birdmom.net/Wildflowers...

Thank you Susan! I think you're right on about the photo being a match. Glad to see another pic. The Mimulus ID is a puzzler for me, too. I took photos of the seed pods and will plan to post them tonight.

If I were smarter and could fill in more of the characteristics, it seems this would be a useful key: http://www.colby.edu/info.tech...

Good; maybe photos of the seed pods and seeds will help nail down an ID!

I've been trying to figure out what kind of a flower that is for a few weeks now! I had one come out of a "wildflower mix" no idea what was inside since it wasn't a traditional seed packet.
As crazy as this sounds is it possibly a form of baby's breath?

Hmm, interesting! The Gypsophila (Baby's Breath) images I pulled up online did include some plants with similar-looking flowers and flower buds, but the flowers had much longer stamens than this mystery flower. On the other hand, I see that there are many more Gypsophila species than I would have ever imagined, and I admit I don't know enough to rule it out.

Yes, the Gypsophila idea is intriguing. It seems these might fit somewhere in Caryophyllaceae. Here are pics of the seed heads. I clipped them for fear they might spread all over the yard before I found out if they were good/bad. The pods haven't opened yet. I'll try for pics of the seeds and opened pods if the mystery still persists.

The seed pods do remind me of Silene. Maybe Lychnis coronaria is a closer match.

I agree with you Christine about the similarity of the seed pods to L. coronaria. It's what made me lean toward Lychnis/Silene. The leaves on this unidentified plant are smoother (maybe entirely smooth) and bright green.

The closest I've found is Silene antirrhina but while the seed pods are very similiar, they don't quite match up as well as I would hope.

Maybe Vaccaria hispanica? Both the leaves and flowers look like good matches.
https://gobotany.newenglandwil...

http://fieldguide.mt.gov/speci...

Wow Susan! I do believe you're right! Thank you!

Many thanks also to Kat. This site mentions the similarity between the two plants: https://uswildflowers.com/deta...

You're welcome!