Genuflected Greetings and Salutations all! So... been hankering usage of more superlative sprites for laconic exemplification; Inverted Podoboo, Mouser, Pendulum Sprites etc. But this irksome admonitory message reiterates itself. If anyone could elucidate befuddling erratum of why? I'd be appreciatory, cheers!
If you took the SMWcentral version of Mouser, it's for Pixi, so it's very probable that this is the problem.
Overall, I'd recommend to try with Pixi. Pixi comes with a converter to insert Sprite Tool's sprites, so you won't lose all the Sprite Tool sprites that you wanted.
PS: where did you find the inverted podobo? Can't find it anywhere, I'd love to have that sprite
Super Mario Pants World
Luigi's Lost Levels
New Super Mario Pants World
Luigi's Lost Levels 2 - Back With A Revenge
Luigi's Lost Levels 3 - Electrik Boogaloo
VLDC12 - 72HoKaizo#1