The foreign language they speak in Pokolistan appears to just be Bulgarian.
The Old Woman watching the Frankenstein mansion has a real picture as her phone's wallpaper, a shirtless Zac Efron at the 2014 MTV Video Music Awards (2014).
G.I. Robot says he's been waiting to kill Nazis (with a friend) for 74 years, 23 days, and 52 minutes. Presuming this is set to take place around when it initially aired, this means he last killed Nazis (or killed Nazis with a friend) in mid-November 1950, a little over 5 years after the end of World War II on Sept. 2, 1945.