Brain's Disguises: Ice Cream Man, Coyote and a Buzzard
Even though Penny implied that she would be getting into her swimming suit because of the heat, she stays dressed in her typical long jeans and tee thoughout the epsiode.
Many times in past episodes, Dr. Claw has various cameras spread out that somehow keep an eye on Gadget. In this episode he actually has one inside the Gadgetvan that is watching Gadget.
Gadget: (diving off a modified chair from the Gadgetvan and into the swimming hole) Last one in is an old stick in the mud. Go go gadget legs! Whooooo-huh?
Penny: (exiting the Gadgetvan) Uncle Gadget...are you alright?
Gadget: (laying in the dried up pond covered in sticky mud) Make that first one in is an old stick in the mud.
Gadget: (coming in from outside with empty water bottles) It's a good thing I filled up these water bottles. The Gadgetvan was filthy.
Penny: (sharing a fan with Brain due to the heat responds in disbelief) You used the water to wash the Gadgetvan?
Gadget: (proudly) Of course, I have an image to think of.