Mr. MacTaggart is a Scottish terrier (in both breed and nationality) who appears in the Dog City episode "Radio Daze." MacTaggart is a television repairman hired by Eliot to fix his set, but the old dog has complete and utter disdain for the medium, which he claims has nothing worth seeing (save The Adventures of Ace Hart, of course). He longs for the golden age of radio, inspiring Eliot's plot.

Mr. MacTaggart also inspires the character Rusty McCracken in the cartoon segments.