(to Snoopy) Rex! You naughty dog, Rex!
Source: Snoopy, Come Home
Note: This occurs as Snoopy and Woodstock try to flee from Clara during a extensive chase sequence across Clara's house, and finally succeed when a fishbowl falls over Clara's head and gets stuck. Not technically dead, but considerably discontinued as in the comics for the similar character Marcie, who appears in the sequel "Race for Your Life, Charlie Brown". Please note that Clara is calling Snoopy "Rex" because when she found him, she mistook him for a stray (when in actuality he, along with Woodstock, was heading to find the hospital Snoopy's previous owner Lila was at).