When Granny says that the soot sprites are probably holding a meeting to decide whether they want to reveal themselves, the scene cuts away to the soot sprites having a meeting in the attic!
Kanta teasing the girls.
Kanta: Hey, you in there, your house is haunted!
Kanta: (runs away)
Most scenes with Kanta and Satsuki. The terrified look he has on his face nearly every time he sees her is priceless, and the way he smiles and skips after he gives her his umbrella is adorable.
Pretty much any face Totoro makes is hilarious.
Totoro's bewildered amusement to rain drops landing on his umbrella.
Also the fact that he stomps the ground making a heavy rain fall upon him and Satsuki, and smiling cheerfully the entire time.
Mai's first interaction with Totoro. Rather than be frightened of this giant furry beast, she opts for curiously inspecting his tail by playing with it, then petting it. Then she laughs with delight, hugs his tail, then eventually ends up on his belly after he rolls over. When he roars at her, she isn't frightened, either - she roars back in the cutest way, then bursts into laughter. It's simply adorable.
In a Meta sense, how about the fact that Troma Films, released a early English dub of the film, granted under a different name. Remember, Troma released THE TOXIC AVENGER.