it took me a minute to see the 2 different plants.
the first i thought was rose champion, but the flower didnt match..then i noticed the slug (nice specimen, lol) and saw the different leaves on the bottom right.
i think the smaller plant (with the flower) may be an impatience. im not sure if i spelled that right.
Oh, golly, folks. It can't be impatiens or aster for that matter. I didn't grow either from seed. Could it be Erinus alpinus? I did grow that. Its common name is alpine balsam, so if it looks to you all like impatiens and balsam IS another form of impatiens, then maybe it is the Erinus.
Sorry to disappoint but it is an Impatiens, Erinus has a much smaller flowers with lance shaped sticky leaves, and is in the Scropulariaceae family (foxglove family, its common name here in the UK is fairy foxglove)
Impatiens walleriana is in the Balsaminaceae family and is most certainly what you have there. It may be that it came in from somewhere and self sown itself.
I agree with Baa and all that said it was an Impatient. I have them all over my greenhouse and the seeds furl all over the place . They will come up everywhere . I don't know how it got there regardless if you didn't plant it. That is what you got. I could not believe the audacity of that slug to just pose for his picture after he ate big holes in your plant. Give him a shot of beer quick. lol
OK, I buy it. A self-sowed impatiens. Oh, well.
The slug is on the lower left leaf. Big as life. I didn't see him when I was taking the pic or he would have faced instant death.
Congrats to all you wonderful knowledgeable plant identifiers. As soon as I decided you were right, I checked my hanging baskets and of course that's what it is.
Now my face is purple, not red.
Thanks again, all.