How Obvious?

[Miss_Understood]

Wow, great job. The average party photo collector, as I call them, would never pick it out. However, if you have a trained eye and really stare, there are things that give it away:

(not in order)

You're crooked. This is the one that draws the eye the most, I think. The photo was taken at an angle, but you two look to be standing on perfectly level ground. Rotating would definitely help.

You're too in focus for the depth of field. I know you blurred it, but a little more wouldn't hurt. This is subtle though, so I wouldn't worry.

You're shoulder seems to have its own light source. Now granted, if you were actually there, light might still hit the spot, but it just seems telltale right next to someone's head.

That same shoulder/arm is blended into the blue shirt of the guy in front of you. maybe you didn't erase quite on line?

The skin of the inserted photo is giving off this pinkish hue that I can't place, but doesn't seem to be in anyone else's skin (like, the skin tones that show up due to the lighting of the room.) Color adjustments maybe?

That's all I really caught (and that was with intense staring). Most of these, like I said, I wouldn't worry about two much. You're eye sees it much clearer because, like you said, you made the add. Nobody else notices quite as much. =)

[Chica Loca]

I would say that it is the guy kneeling on the right and the lady in back with the short blonde hair.