In "Clownus Interruptus", Molly tries to get Loonette's attention when the latter is on the phone. Loonette finally has it when Molly blasts an air horn.
In "Ping Pong Polka", Major Bedhead gives Loonette a special package from her aunt, which turns out to be full of ping-pong balls.
Loonette: (as Major Bedhead unties the box) Be careful as you open the box, because...
(Major Bedhead holds the box upside down and it opens, and they all fall out from in the box. Cue awkward silence.)
Loonette: You don't want them to spill on the ground...
Later on, after picking all the ping-pong balls up from outside, Loonette winds up tripping on the mess she made earlier while showing the box to Molly and spilling the balls again! And just to drive the point home, after returning from Dance Academy she winds up tripping on the balls themselves.
The episode "Backwards!" is about an entire backwards day, leading Loonette to make a mess of her room at the end instead of cleaning it up.
The entire "Rude-I-Culous," "Give Yer Head a Shake" and "Why?" episodes for Molly's antics in being rude, constantly saying "no," and constantly asking "why." Usually the characters are very sweet, so when they aren't, it's funnier than it should be.
Loonette accidentally scaring Molly with her mask in "Scaredy Cat". Especially Molly's reaction when Loonette comes up to her in the mask, while Molly is knitting, and the way she slowly looks up in realization and then towards Loonette's face before dolting under the pillow is pretty funny.