The War of the Simpsons - S2-E20
Continuity mistake: When Homer has caught General Sherman he beats it with an oar so that the oar snaps in two. Then suddenly Homer rows with both oars intact.
The War of the Simpsons - S2-E20
Continuity mistake: When Homer has caught General Sherman he beats it with an oar so that the oar snaps in two. Then suddenly Homer rows with both oars intact.

The Simpsons Christmas Special: Simpsons Roasting on an Open Fire - S1-E1
Continuity mistake: Lewis changes from black to yellow when Milhouse dares Bart to pull Santa's beard off. (00:14:10)
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)?