Reptiles in the Rose Garden - S1-E1
Factual error: After the White House is teleported to the Mushroom Kingdom, the President can be seen still using his phone, but it would not work as it would be disconnected from the landline. (00:03:44 - 00:07:19)
The Secret of the Unicorn: Part 1 - S1-E3
Factual error: The man selling the Unicorn tells Tintin that he can have it for 25 dollars. Tintin is Belgian and this is in his home town; they should be using francs in that time period. (00:03:30)
Factual error: There's an exhibit in the Smithsonian Institute that shows Benedict Arnold, William Demont, and Major John Andre labeled as Famous American Traitors. One problem, Andre wasn't a traitor to America as he was a British officer to whom Benedict Arnold arranged to surrender West Point to during the war.
Cell of Iron - S2-E3
Factual error: When Iron Man is floating away from the asteroid after his thrusters and repulsors have malfunctioned, he somehow comes to a dead stop in the vacuum of space. (00:07:27)
Welcome to Brickleberry - S1-E1
Factual error: Malloy has been missing all day and is starving from not eating. Yet his cheeks are sunk in like he hasn't ate for weeks. Your face doesn't get like that after not eating for a day.
Factual error: Brozzi asks for Lupin's help saying that the final of the Coppa Italia elimination tournament is in 3 days. He just played a game winning the semifinals, though; there is not, and never has been, such a small interval between the final stages of the cup. (00:06:20)
Factual error: Squirrels are seen woken from hibernation along with other animals, but squirrels don't hibernate.
What If... Captain Carter Were the First Avenger? - S1-E1
Factual error: When Stark starts telling about the Tesseract, the colonel shows surprise that Nazis were in Norway. Peggy answers with "Close. HYDRA." The scene is set in 1943, and Norway had been occupied by Nazi Germany for three years already. Them being in Tønsberg should not come as a great surprise to an Allied commander. (00:07:10)
Suggested correction: I feel like this falls under the "Not a mistake because it's an alternate universe" umbrella. We're in an entirely different universe with a different timeline in this episode.
The show also makes a point that the only difference should be the minor choices or events befalling the MCU characters, and how these minor things have huge consequences for them, basically creating a new alternate timeline. Basic world history before these events is not affected by the new timeline.
Basic, unaltered world history does not apply with this because we are talking about an alternate WWII from the beginning. One with Schmitt/Red Skull as propaganda minister of Hitler, Hydra superseding the SS, super soldier serum, Stark tech, the Tesseract, etc. It is not WWII as we know it, even without the "what if."
Factual error: The forces of Cassiopeia all sport the crown-like "W" sign which is the shape of that constellation... but only as seen from earth! These five points in three-dimensional space (like all star signs named after anything) look like that when viewed from our own planet; but from anywhere else, they aren't shaped like that at all. Why would they chose to see themselves through a very specific angle of view from some other distant planet (earth)?