Rednecks and Broomsticks - S21-E7
Continuity mistake: When the Simpsons are on the highway, Apu's car is seen, and some of the octuplets have yellow skin and blonde hair.

Rednecks and Broomsticks - S21-E7
Continuity mistake: When the Simpsons are on the highway, Apu's car is seen, and some of the octuplets have yellow skin and blonde hair.
Skinner's Sense of Snow - S12-E8
Nelson: Hey, look how much Skinner makes: $25,000 a year.
Bart: Let's see, he's 40 years old times 25 grand. Whoa, he's a millionaire.
Skinner: I wasn't a principal when I was one.
Nelson: Plus, in the summer, he paints houses.
Milhouse: He's a billionaire.
Skinner: If I were a billionaire, why would I be living with my mother? [All the kids laugh at him.] They're just not responding to logic anymore.

Trivia: Maggie scans as $847.63 in the supermarket at the beginning (not NRA4EVER, as Troy Maclure asserts in 3F31 "The Simpsons 138th Episode Spectacular), the price it costs to feed and care for the average American baby every month.
Question: Which episodes feature the "Howling Dog" (usually used on outside shots of buildings)?