I've suspected this recently due to noises but just heard the clatter of the food bowl being moved around and happy chirping noises that don't sound like our cat RooRoo, as I go downstairs other big tabby rushes out the cat flap but stands on the other side of it rather than fully running away, our cat then casually saunters over from the sofa to see what's going on! Is this normal for him not to react, he didn't seem scared. Any advice how to stop this cat coming in, I don't want to be paying to feed someone else's cat and we had an awful time recently of cracking a flea problem and just yesterday noticed the buggers are back, now I'm thinking it could be down to this other cat! Btw it didn't look stray looked healthy and v well fed!