That can be accomplished by using a version of a pet name (or “pet” name) with some letters substituted with special characters (”i” with “!”, “o” with “0”, “a” with “@”, “e” with “3”, etc.).
The great thing about my wife is that she comes up with completely random but memorable names for our children. Like “Melvin”, when neither of my sons is named Melvin (don’t worry, I’ve never used “Melvin” nor any version of it for a password, it’s a completely made-up example).
I just look around and let my eyes come to rest on some object and use that as the basis.