Frogless has actually been proven possible, if really precise and/or inconsistent. There’s only one wall that’s difficult to climb with groundpound jump, Cappy bounce, Cappy return boost, walljump, Cappy throw, dive - and that’s the second jump in the frog segment so restarts are fine if you miss it too many times.

As an added note, I think it’s possible to get every purple coin in every stage without making any captures that aren’t already required for story progression (based on the fact that I got 46 coins in Cascade, and I think the other 4 are on the painting island). So Purple Coins% no unrequired captures would probably be feasible.

It’s difficult to say. For Super Mario Bros, I’d say take the best run of the fastest known strats, and the worst run of the safest strats (ignoring outliers), and find the median between them for the average time.

For games like Odyssey, where the ‘perfect’ run is still far from being discovered, I think there’s nothing to do but eyeball it. At the moment I’d say that’s around a 1:17 run, but the moment a new strat is found, the average time will jump down a couple minutes.

Mario Odyssey is such a huge game that a “perfect run” can’t really exist for it. There’s always going to be new glitch discoveries, routing, optimisations and so on.

For an idea of how inconceivable an optimised run for Mario Odyssey is at the moment, take a game running at 60 FPS, which when run perfectly, takes exactly one minute to complete. That’s 3600 frames worth of perfect inputs. For an actual game of that length, it might take weeks or months to find the perfect run, depending on the complexity of the controls. Or just 60 seconds if the entire goal of the game is to hold right for a minute.

It might not look like it at the surface, but Mario Odyssey is an EXTREMELY complex game thanks partially to the vast choice of moves, partially to the 3 dimensions of the game, and partially to the fact that Mario Odyssey is incredibly non-linear. Perfecting an entire hour (although I guarantee that a ‘perfect’ run would last under 45 minutes) of Odyssey would take 3600 seconds of perfect inputs (or 216000 frames), with hundreds of input combinations available on each frame, and each input changing the availability of future inputs.

Even ignoring all the glitches that haven’t been discovered yet, finding the perfect hour-long string of inputs from that mess will take more than a decade, probably more than four or five, and that’s with a robot performing the inputs. Humans can’t even complete a game as simple as Super Mario Bros with the same speed as a computer, so the possibility of reaching machine efficiency with Odyssey is so close to 0 that it isn’t worth trying to calculate.

And again, that’s ignoring glitches, which could change the routing in who knows what ways, and are bound to be discovered routinely for the next decade at least.

TL;DR, Odyssey’s speedruns are as close to perfection as the Earth’s core is to receiving a breath of fresh air. Which is to say, not.

EDIT: And for an actual example: Did you know that spinning can be buffered from any animation? This could make it possible to quickly change directions while rolling, allowing it to be used in many more situations; and offer a way to do spin-throws frame-perfectly, and without risking the motion controls not working properly. That simple tech alone could possibly save minutes from a run, and it’s just a basic part of the control scheme.

Now imagine if a glitch was found that let you bounce off Cappy twice in one jump. Congrats, hundreds of new skips just became available, knocking the timer down a full 20 minutes. Cascade kingdom can now be done without even capturing an enemy, since you can just jump over the river and scale the cliff instead of capturing Chain Chomps. Et cetera.

Super Mario Bros 1/2/3/World (although some of those have level select screens).

Sonic 1/2 (3 and Mania have cutscenes although for 3 it might just be the opening one; CD has time travel screens but I don’t think an any% run would come into contact with them). 1 has some super slow segments though, so 2’s probably your best option there.

I think Freedom Planet has a mode where you skip all cutscenes and just play through the levels.

Sonic Heroes. It does have some short cutscenes and fair loading times, but the levels are much longer than the average Sonic game (especially for team Dark) and there are fun glitches and skips littered thoughout the entire game. The most common category is any% because the True Final Boss has a 43 second transformation sequence.

Gutar Hero/Rhythm Heaven? They can’t really be speedrun, per-say, disregarding menus, but you might want to look into all-perfect runs.

Mario Odyssey’s a decent one. There’s sadly a little downtime at the very beginning and I’m not sure the credits are skippable if you want to do 100% runs (although I think given how long that’d take you’d be glad for the break).

Not to mention the ever-classic Mario 64. Sunshine has a really long cutscene right at the beginning though.

Pacman.

The original Legend of Zelda. Also BotW, in a similar fashion. Very few cutscenes are necessary in either of them. BotW any% is a very short run though, so I wouldn’t recommend buying it just to run that category.

Sandbox games like Minecraft/Terraria. Not Starbound, that has a few reaaalllly long unskippable cutscenes which I find endlessly annoying in an otherwise amazing game.

Mario Kart. I’m not sure if the start-of-race and final-placings cutscenes are skippable in all the games, but I think they are in most.

I haven’t played it in literally 10 years+, but I seem to remember NFS: Most Wanted (the PS2 game) being good about cutscenes. In fact I just checked and it seems that only one of them unskippable - the any% WR if almost 4 hours though, so you’d be in for the long haul.

Portal 1/2. 2 has a fair amount of dialogue, but you can still move while most of it’s in effect so you can try out some cool tricks in the meantime. 1 has less dialogue but I don’t think it’s as fun a run overall.

That’s all I can think of for now, hope it’s a good starting point.

If it saves time and looks cool, always go for it. If it loses a little time but looks cool, practice it outside your regular runs and use it as a hype generator for events and such (or even to de-tilt yourself when you really need to do something cool). Showmanship is half of a good speedrun after all.

Just spin the stick and you spin on the first frame that the option becomes available.

I’ve done some testing, and turns out you can buffer a spin from literally any state in the game. This includes bonking, jumping, crouching, going through a loading zone, rolling, etc. - as long as you end up in a state which allows you to spin, you can buffer the input at any time.

The biggest time save that I can see from this is from spin-jumping, then groundpounding and pressing Y as you land to start a roll at maximum speed. It’s also good when you need to make a high jump right after collecting a moon.

I’m not a speedrunner myself so I can’t say how useful this will be; I just noticed that it could be done and figured it could help.