Skyward Revelations was originally going to make the "Skyward" title make more sense but because it was kind of rushed so I get it out between December 14th through the 25th (that was the supposed deadline for the game's release)
Goomy the Almighty started a Skyward comic series in November but he never got past the first page. He rebooted it via DeviantART but it is currently on hold.
Lloyd's helmet was originally going to look more like a bike helmet (back when he was a playable character) but later it was changed to look more futuristic.
Matthew's design was based off of the design of a character Goomy made up for a Fantendo game called Mother 4/Earthbound 2. So now Head will stop with the whole OMG NINTENDO IS GOING TO SUE YOU CUZ NESS LOOKS LIKE MATTHEW!!! thing.
There were a lot of beta characters for Skyward, a lot of which can be found on the page for it on the Sploder Series wiki. There is some time traveler with a weird name that consists all of digits, a boy named Adrian, and a girl named Elise. Elise appeared in Skyward Revelations Remade, replacing Crystal.
The two most interesting of these were Professor Dunce, who has appeared in Skyward but only as a cameo. He originally started as a Mjd Series character, but Goomy used him since he originally created the character. He does make a cameo in Skyward Chronicles Chapter 1, though. Another beta character was one named Xavier, who never appeared in any games nor on the SSW Wiki page. I think he was supposed to be Leo's beta design.
Negativ originally had a different name. I don't remember what it was but it made no sense at all. Skyward was published with him having this name but Goomy eventually changed it.
Skyward Powers had had two betas, both of which were cut from development. One had the same gameplay as the first two games but the other one was 3D, like Tigzon. The current beta is 2D but has 3D backgrounds.
Bob's colors in Cube Fighters and his cameo in Skyward aren't accurate. In Cube Fighters he is light brown and in Skyward he is dark brown. However, in recent art of Bob and in Cube Fighters 2, Bob is blue.
According to Head, Matthew's appearance in Skyward seems to be based off of the most famous Sploderian, Sceptile, which makes a little sense considering his name is Matthew, which is also Sceptile's real life name. But according to Goomy the Mighty, this is all a coincidence.
In Skyward 2, Alex was originally going to be able to hover. This was removed because Goomy thought it would make him too overpowered. Hovering would have been added in Chronicles if it wasn't cancelled.
In Skyward Chronicles, Head3000's deep hatred for Mjd and his series is referenced in the first playable level, where Zack and May can be seen fighting on top of a building. It is possible to jump up there and push May off. If you manage to crush her, you gain an extra life.
The odd concept of Matthew's Quest was based off of a game on Fantendo that Goomy made.
Skyward Revelations Remade was intended to have day-one DLC but ultimately was cut.