Velma's infamous line "I can't see without my glasses!" was originally not in the script. The line was only added after, by coincidence, Velma's voice actor Nicole Jaffe dropped her glasses by accident while reading off the script, and uttered the line in frustration. The writing room thought it was perfect for Velma's character, and later added it into the show, where it soon became Velma's trademark line.
~ WildwindVampire ~