Grandpa has dishes with "1948 - Coney Island", "1944 - Miami Beach", "1936 - Pike's Peak", and "1932 - Los Angeles", although the 1932 plate originally had a date from the 1940s.
The episode takes place during an "Indian Summer" (according to Phil). An Indian Summer is a warm period during the fall months.
At first, Mitzi says they hadn't spoken in 70 years while Grandpa said 71, but at the end, they switch numbers.
Mitzi and Gertie are girlhood friends, since Gertie mentions that they had sleepovers when they were girls.
This episode is "dated", sort of; since the day they stopped speaking to each other (November 13th, 1927) is either 70 or 71 years ago, so it must take place between mid-November 1997 and mid-November 1999.
Just after the mousetrap scene, Monkeyman runs outside in front of the Sunset Arms.
When Grandpa tells Arnold that he put laxatives in Mitzi's yams, Mitzi is eating yams, despite claiming that she spooned all of them onto Grandpa's plate.
If Mitzi owns half of the Sunset Arms, how did Grandpa try to sell it without her permission in the episode "Casa Paradiso"? It is possible that Mitzi's statement ("This house is as much mine as it is yours") was more intended to remind Phil that she grew up in the boarding house just as he did.