Seedlings are hard to identify. Their leaves often look quite different than a plants mature leaves. It does rather look like it could be an Eschscholzia species though. (California poppy)
http://www.wildflower.org/gallery/result.php?id_image=20267 just out of curiosity, don't these plants look different? http://i464.photobucket.com/albums/rr4/earthfriendly13/100_0738.jpg
The first link shows an older plant, but one likely grown in cool conditions with bright light, which gives denser foliage with smaller leaves.
The two plants look very similar to me. As mentioned above, leaf form and general plant form varies with age and condition. Sometimes two individuals of the same taxon can look quite different. There are several species of Eschscholzia. You may have a different species there, but I would still guess California poppy. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=112192
