Option #1: Try to emulate an existing font or just invent some silly sort of writing style. You could add arrows to each letter... or bubbles or rainbows! The pink swirly doodles were already on the pages of my lined journal; you can add some sort of frame if you are in the mood.
Option #2: Write the alphabet over and over again, overlapping, with variations. Write while you are not looking at your journal page. I wrote the letters of the alphabet on the second page above {this is in my Art Doodle Love journal, pg. 91} while watching Boardwalk Empire. I couldn't see what I was doing other than to feel the overall edges of the book.
Option #3: {Disclaimer... I've not tried this} Cut out as many variations of one letter as you can find in one magazine. For the sake of your eyesight and hands, focus {no pun intended} on headlines and larger letters. Glue them into your journal or put in a little glassine envelope and attach to the page. It just sounds so cute.