Try this yourself! Use Game Genie code ATVPTTXZ (in an emulator, Everdrive, or real genie).

Eerie playing the game Trog! without any trogs in it. Note that (a) when Trog is inventing new moves, he draws a blank, and (b) there is no way to finish bonus waves like the Barbecue! level (see 3:25) early, you have to run out the timer

I crafted this hack while working on navigating the game's disassembled source code (in order to create hacks like this one). The files I'm working up to annotate the sources are at https://github.com/micahcowan/trog-patch. More Trog! hacks to come!