I realized this while using reset abuse but it still applies when not using it so i figured i would share it. It seems that the gates do not unlock by use of the keys but actually by defeating the boss itself. For example Skelord's gate in ice world will open once he is defeated even if you don't pick up the key. This could save a few seconds in certain places in any% so it could be useful to know. Same concept applies to events so this also works for Ludo, Lil Fatty and the Jetpack key (same would probably also apply to the other keys but there is no way to avoid the key for those). I, however, would not suggest skipping Ludo's key as it seems the quick fly mechanic is given to you upon picking up Ludo's key.

Did a bit of research on this and for Any% there is one key you definitely want to skip. Not important for the others though.

Ludo's Key: As stated you don't gain the ability to quick fly if you skip this.

Skelord's Key: This is the gold right here. As soon as you kill Skelord, quickfly back to the hub. Saves you 5+ seconds.

Fatty's Key: You can skip this for the memes, but doesn't save any time.

Cracker's Key: Can't skip this as it acts as the quickest way to get to Tower.

Tower Key: So, I discovered that you can quickfly immediately after finishing tower and you get the key anyway.

Space Key: Unskippable.

Skelord and Tower key new strats have helped me shave about 10-15 seconds off the record, but the fun happens if you were to backpatch to 2.0 and do an Any% Reset Abuse run. This is theoretical for the moment but this is a Any% Reset Abuse 2.0 run:

• Skip Ludo's key (or don't, I'm not sure which next step would be quicker overall)
• Get double jump
• Reset Abuse back through Spookelium to the hub OR quickfly, depending if you got Ludo's key or not
• Reset Abuse all the way to the base of Tower
• Reset Abuse through the Tower gate and complete Tower
• Go to and complete Space
• Go to Mirror World and Reset Abuse your way to float
• Kill Float
• ?????
• Profit

No Ice World or Castle needed.

I have tried to reset abuse through the tower gate and i believe it was one of the screens that it didn't work on.