3. The Resurrected Dr. Nick And Dr. Monroe
Dr. Nick Riviera, Springfield's most friendly incompetent doctor (say it with me now, "Hello Everybody!" "Hi, Dr. Nick!") was impaled by a large shard of glass from the destroyed dome in The Simpsons Movie, but showed up in the regular program again in "Lost Verizon", with his character's apparent demise going completely unmentioned by the citizens of Springfield. Ditto the unloved character Dr. Marvin Monroe, psychologist to the Simpsons family in the 1st season episode "There's No Disgrace Like Home", who despite having a memorial hospital named after him in "Who Shot Mr. Burns (Part 2)" and his grave being clearly shown in "Alone Again, Natura-diddly", reappears in "Diatribe of A Mad Housewife" with no other explanation than a throwaway joke ("I've been very sick."). Other characters who have died over the course of the show, like Maude Flanders and Bleeding Gums Murphy, have remained dead, so what's so special with these two?