¡ʎɐqǝ uo pɹɐoqʎǝʞ ɐ ʎnq ı ǝɯıʇ ƃuı…ɟ ʇsɐן ǝɥʇ sı sıɥʇ
It’s stupid but cute. In the extended alphabet sets of, there is a vast selection of letters. Among these are those that can be used to model normal english characters upside-down. This site has a script for converting text and a key of each character’s representation.