Er, this was a mistake. My bad!
I had my TV set on "16:9" but forgot to turn the "Wii U Widescreen" option off. With the option off, the black bars only get smaller instead of getting cut off, but the top and bottom is still cut off.
Okay, I'll list one game from each category. When testing, these games were all played with the "Wii U Widescreen" option off (So 4:3) and my TV set on "Screen Fit." ("16:9" was the same as "Screen Fit" but stuff was cut off.)
Amazing Island: Has both circles and ovals. In dialog boxes, the green rectangle prompt is supposed to be square, but when you go up to someone, the A Button prompt and the square cloud it's in are fine. A quick Google search showed that the A Button prompt and the square cloud box are supposed to be a little wide, so when I said that some games have both, it was indeed because of a developer mistake, so we can conclude this game is squished for me.
The Incredible Hulk: Ultimate Destruction: Has both. It looks fine when it has both in-game Widescreen and the "Wii U Widescreen" option on. It looks squished with both off.
Scooby-Doo! Night of 100 Frights: Has ovals This one is mind-numbingly obvious, right as soon as you see the Heavy Iron Studios logo. Other instances include the moon, and the characters looking anorexic.