- Film Appearances: Johnny Thunder and the Wisdom of the Ancients (cut from film); Johnny Thunder and the Trail of Botnik
- Character Role: Sidekick
- Actor: Jummie
- Character Sex: Female
Gertrude Dainman has a head of dark brown hair, which is styled into a bun that sits high upon her head. She usually has a confident smirk, though is not unheard of to be easily shocked, though not scared.
She wears a dark orange vest with a white undershirt and carries a walkie talkie in her back pocket. She has a cell phone tucked into her front pocket and wears a set of straps for carrying field equipment. She wears dark blue pants.
Gertrude is a well-educated, ambitious archaeology intern at the LEGO City Museum of Natural History who aims to prove herself to her peers, especially the world-famous Johnny Thunder. While she sometimes can get ahead of herself, she is also alert and calculated, able to understand ancient warnings and writings.
- This character was actually recycled from a cut character from Johnny Thunder and the Wisdom of the Ancients, though her role was vastly different. She was intended to be the love interest for psychic Steven Sever, but was removed for being a pointless character. The only existing details for this version of this character are in preliminary files for the film. She was the first character to be cut out of the film.
- Just like Sarah dating Lance, this character was intended to add romance to Mustache Manaics Film Co.'s animated films, something that they were noted for lacking. This trait, however, was not used in her canon role in Johnny Thunder and the Trail of Botnik.