Pages:
Smile Dippin' (Maybe I've had too much) / My kidneys (?) (mouth overflowing)
This Guy! (gnome barfing) / Bad times (tied down) / Wheeee!!! (golf cart crashes)
Pioneer Day (statue picks Mabel's nose, Stan in stocks) / This happened (cow out of car window at beginning)
Who's this joker? (space lizard) / Best friends! (Mabel and the dogs) / In Yo-Face! (Mabel and Dipper w/ trophy, lizard trapped in snow)
Octavia, the 8-legged cow, has 9 legs
carny - same guy who gave Waddles to Mabel
Does this mean the carny remembers Mabel, or vice versa? Put this together with the next clue and you get a theory that Waddles could be a mutant.
Northwest mud flaps - toxic sludge - mutant animals
A couple things here. First, the factory is called "Northwest Mud Flaps". It could be referring to the region of the US they are in, or more likely, it means the factory is owned or at least sponsored by the Northwest family. Makes sense, considering their wealth and prestige in the town.
Second, I think I figured out what the toxic sludge does. It gives the creature an extra of whatever body part touches it. The goat drank from the river, and it grew an extra head. Octavia would have, then, walked into the river. She took 5 steps in it, hence her 9 legs.
Warm up the truck.
How does the carny not hear this?
Emmitt & D'Shawn
Characters with the exact same designs are seen on the Phineas and Ferb episode "Last Train to Bustville".
Serves me right for building an escape ramp.
She was alright for a mutant.
Stan says this line at the end. It gives me the impression that Stan has met multiple mutants. This ties in with the fact that he knows a lot more about the secrets of Gravity Falls than he's letting on.