Plot hole: In "The Conners" premier, Dan solely blames neighbor Marcy Bellinger for Roseanne's death after finding a bottle of opiates with Marcy's name on it. He only relents after Darlene shows him additional opiates that other people gave Roseanne and were hidden around the house. However, in the Season 10 reboot of "Roseanne", Dan had previously discovered and confronted Roseanne about her multiple opiate stashes, including one bottle with Marcy's name on it which he read aloud.
Casualties - S2-E14
Plot hole: When Bradford and Chen arrive at her apartment to see the damage her newly adopted dog did, she discovers the dog ate her roommate's varsity jacket, but she had to turn the doorknob to open the door; there is no way the dog got into that room if the door was closed.