I look for this part of NickJr.com every year, so I decided to pin it so I didn't have to search around anymore. This is their Custom Printable page where you can choose your product (card, bookmark, etc.), character, and colors. Then you type in your own message, complete with your hcild's name on it. Pretty sweet for a birthday party or sleep over for pre-schoolers. :)
This site has tons of free printables from all of my son's favorite shows - Team Umi Zoomi, Wubbzy, Bubble Guppies, Including chore charts, daily routines, birthday party items, activity sheets as well as books!