Nothing to Escape

What is your wild guess: How many different ways does Ruby provide for inserting a NULL byte into a double-quoted string?

There are exactly 43 options┬╣! Here is the list, put together with some ideas from Episode 61: Meta Escape Control:

Directly embedded NULL byte # => "\u0000"
"\0" # => "\u0000"
"\x00" # => "\u0000"
"\x0" # => "\u0000"
"\u0000" # => "\u0000"
"\u{0000}" # => "\u0000"
"\u{000}" # => "\u0000"
"\u{00}" # => "\u0000"
"\u{0}" # => "\u0000"
"\u{00000}" # => "\u0000"
"\u{000000}" # => "\u0000"
"\000" # => "\u0000"
"\00" # => "\u0000"
"\C-\0" # => "\u0000"
"\C-\x00" # => "\u0000"
"\C-\x0" # => "\u0000"
"\C-\000" # => "\u0000"
"\C-\00" # => "\u0000"
"\C-@" # => "\u0000"
"\C-\x40" # => "\u0000"
"\C-\100" # => "\u0000"
"\C-`" # => "\u0000"
"\C-\x60" # => "\u0000"
"\C-\140" # => "\u0000"
"\C- " # => "\u0000"
"\C-\s" # => "\u0000"
"\C-\x20" # => "\u0000"
"\C-\40" # => "\u0000"
"\c\0" # => "\u0000"
"\c\x00" # => "\u0000"
"\c\x0" # => "\u0000"
"\c\000" # => "\u0000"
"\c\00" # => "\u0000"
"\c@" # => "\u0000"
"\c\x40" # => "\u0000"
"\c\100" # => "\u0000"
"\c`" # => "\u0000"
"\c\x60" # => "\u0000"
"\c\140" # => "\u0000"
"\c " # => "\u0000"
"\c\s" # => "\u0000"
"\c\x20" # => "\u0000"
"\c\40" # => "\u0000"

┬╣ And this is just in the context of double-width strings without interpolation: Another fun NULL byte is 0.chr, as noted by @cremno

Also See

More Idiosyncratic Ruby