Danielle, I am curious to know if you have knowledge about clip art copyrights? I am looking to create a few things, but am unsure about copyrights in regards to clip art. You created Phineas and Verb by using Phineas and Ferb clip art, so I thought you might be a great person to ask! If you do not know, that is okay, too. I have been searching the web for a chunk of time and then had the realization that you might have some information. I suppose it could be just a statement labeling who holds the copyright. Thanks!
I try to find the source and adequately cite where I found it. Oftentimes it has spread throughout the web and therefore, I site where my particular version came from. I'm also always prepared to need to change a material if the image is requested to be removed. However, as with most works, adequate citations of original creation/location will suffice. Hopefully that helps a bit, I know copyright is tricky, particularly as access to various materials increases with google/pinterest, etc! Good luck, I look forward to seeing your creations!