I’m asking this because I recently got my hands on a Fujifilm Discovery 90 and bought some new Fujicolor ISO 200 Color Negative Film from Walmart to go along with it. I would like to know if its compatible before I open the packaging.
The only "incompatibility" you might encounter is the lack of DX coding on some modern film cassettes for a camera that depends on DX (like some '90s vintage point and shoot models) without having any provision for manual ISO speed setting and an inconvenient default speed.
With very old cameras (or fixed-settings types, "focus free" and no aperture or shutter control), you might also run into limitations on the film speed the camera is designed to use (likely ISO 50-100 for pre-1960 models, or ISO 400 for those newer than about 1990) and the film speed you actually have.
Physically, however, any 35 mm camera from a 1930s vintage Leica or Contax to a brand new Kodak H35 will accept the standard cassettes and the film will be compatible with the advance and frame counter system, assuming everything is in good condition and functional.