Critique - Who Am I??!!

Alright, here some notes, old man first:

He seems pretty good although floaty til 182. Be careful not to have his arms or other parts of his body move like he was underwater or in space (for instance the turn away at around x145). Even someone who just stands there needs to have wait.
Make the inbetween poses as appealing as the main ones. Take x220, that seems a bit too big and unappealing for the old guy. I would keep his poses contained so that there is more contrast between him and the detective, even though the detective is soooo over the top, a contrast is a given :)
Put the detail throughout his whole body, including the fingers. x234 got a very extend thumb on the screen left hand and overall could be a nice pose (what's his attitude right now? Just confused? A bit angry? Probably both, so I would make him tense but not have full on fists for instance). He then gets very spliney/floaty til x321. Get off your chair and move exactly like he does and you feel how awkward it is. Act the old man out, film yourself (or someone else), observe grumpy/confused old people? How do they move? You also keep the hand poses (especially the his right with the extended thumb) throughout this time, give it more complexity.
Common mistake during x278 and x300, the whole upper body/arm/head part moves as one block, which looks very robotic. Same here, act it out, does that feel right? It happens before, from 250 to 270, but there the head is at least independent. Another one at around 380 to 390.
The floaty-ness continues with a very weird and slow body-down from 390 to 410, with his head stuck looking up, then absolut slow motion til x441.
Watch "Geri's Game" for reference of how an animated old man moves (even though your not "supposed" to look at animated stuff for reference), but again, act it out, find a friend who acts it out, ask your grand father, find an old hotel valet guy in the city, youtube, bbc motion gallery, movies, etc. Study reference for movement and timing.

Ok, detective guy.

Zoom out, or lower the camera, or move the detective up a bit (or further away), anything so that his foot is not cut off like that framing wise. It's an awkward start. Just tilt down with your camera, you have enough top space.
First pose on x0 is off balance (he'd fall to the left). So either move his body to the right or have him go immediately into the step towards the right so he's not staying in this pose for long. The pose itself is a bit awkward (mainly his right leg and how crooked the foot is). Stand exactly like him and you'll see what needs to get fixed because you'll feel how awkward that stance is.
Same robot movement feel like the old guy from x0 to x7. The whole upper body moves as one piece. Break it up. Think about what part of the body is leading? What is dragging?
Look at x34, that's also a weird pose. Yes, your character can be weird, but the poses still need to be appealing. The way you can't see his left knee and right knee and how the hand just hangs next to the right leg makes it at very weird silhouette.

[pic is coming, blogger is having problems]

The move towards the old buy is better. Watch out that you don't have things moving at the same time, the same way, like his feet at around x105.
The way he looks up in different spots is good because there are holds, it's not always moving.You might want to move out his right arm at around x154 for a clearer silhouette (so that the hand is not in front of the body). To make it read really well you would have to have the detective more screen right and not in front of the old guy. Imagine you would have just the black bodies in your shot (hit 7 in Maya for that) and look at how the two characters overlap. It would be clearer for the audience to have them separated. You have all that space on your right, there is no need composition wise to have them that closely (easy way to move them apart is to move the old guy to the left, so that you don't have to redo the steps and placement of the detective, there is less to do on the old guy).
Again, check your poses for the rest of the clip. Take x204, the way his hand is rotated back hurts. You also have to get in there and get rid of that default finger position, pose your character all the way at this point.
During the steps back avoid overextension of his legs.
From x238 to x246 for instance it's too much of going from pose A to pose B, everything moves at the same time. Would you move like that? Same with x265 to x273 and the forward bend after that. His swing is too fast during the x300+ part. It's okay in layout and blocking (even in blocking though you should flesh out the timing), but so far into the animation process it looks too cartoony (the rest of the movements seem pretty realistic, so that part stands out as "wrong"). Act it out, time it and change your animation accordingly.
Form x310 to x380 everything is constantly moving, hold a few poses (for instance at around x362 for the "Ha!").
The end is muddy as well. Check x383, he looks like a twisty tie :) That pose needs to be clearer and more appealing (and his foot is sliding), same with x422+.
The quick movements after that also have weird inbetweens. Plot out your arcs, give the animation some rhythm, really work on your poses. During fast action like that you will have to go in there frame by frame. Something like his right foot at x431 should not be in there (you need to rotate the foot down).
The roll is also messy, that needs a lot of clean up, especially foot contact (your feet are sliding all over). And really work on thought out hand/finger poses (get rid of his default hands for your next revision).

Phew, lots to do. :)
Keep going!