It's the little things that make a filler episode enjoyable. Like Ash and friends being creeped out and trying to think of what is going on in the mansion. Clemont is scared out of his mind but tries to convince himself and the others that there's a reasonable explanation, followed by Serena saying something crazy and making everyone feel worse multiple times
I also agree with Supersonicbro that TRio was pretty enjoyable in this episode to me. Also I was laughing at James yelling at Meowth that it wasn't the time for jokes as they're running from Espurr because Jessie said something about a cat monster and Meowth said he's supposed to be that or something.
Espurr was also so adorable in this episode. The perfect amount of cuteness and personality. A nice episode to watch every now and then