This clip is really great! The timing is awesome, from the little antenna down to the broader moves.
The beginning antenna part up to around x81 when it disappears is great. My only nitpicky thing would be around x22. The antenna is controlled by the guy and it's very purposeful during all the moves, but when it comes down at that point, with that rebound, it feels like it's just falling down and bouncing, which makes it less intentional and more like a loose object. It's obviously not a deal breaker, but just a tiny bit out of character thing. If you ask WHY is this antenna around, then judging by the anim, it's to observe the area and the timing suggests precision. I would also have it disappear a bit faster, take out 2 or 3 three frames, almost eliminating the upwards move of the red light part. Right now the entry is pretty much taking as long as the exit. Since the antenna checked everything, it can hurry to get to the point. So I would add the 2 or 3 frames you're taking out of the exit to x62, like it's taking on last long look, then it quickly disappears.
Some stuff will change once you go more into spline mode. For instance how the lid gets pushed up and to the side is a bit fast. Especially from x96 to 97. It's a one frame move and makes the object look very light. Give this enough weight while maintaining the cartoony-ness.
The screen left leg on x113 is a bit unclear silhouette wise. Careful about foreshortening limbs. The thigh/knee part is bent towards us in front of the hip, so when you squint, it looks like a short leg. Yet the screen right one is much longer. That one is a tad too bent backwards, breaking the knee joint. Once you spline it out and it's over one frame, such a broken joint frame could work, but right now it's on there long enough to register, and it makes for a weird silhouette.
The entrance of the guy could be a tad faster (up until around x130), for a snappier surprise reveal of who was behind that antenna. Once he hits that pose around x130, repose his right arm a bit. Silhouette wise it gets lost in front of the blue body. Since everything is blue-ish and dark in this shot, silhouette is very important. Same goes for the pose around x180. The screen right arm gets lost as well. Either move is out screen right so it's a silhouette in front of the wall, or make it clearer in front of the stomach, so you can get a color on color silhouette.
For more about that, see this post for example:
Clear silhouette - confuse your audience
Power of silhouette
I love it when he puts the lid back on top and waits right before he does, checking again if the coast is clear. Nice touch! I also like how he puts his hands flat down before the turnaround.
The poses from x293 to x312 need to be stronger. During that section he feels a bit casual. The stealthiness and careful nature is gone, it's another weird character break. It looks more like an athlete getting ready for the jump and roll. The jump and roll is great though. Another moment where you break the joints, but this seems fast enough for me and I think it works better than the entrance of the guy.
The last antenna thing has the same bounciness like at the beginning, which I mentioned before. Again, I wouldn't do it (feels more like it's there for cool animation than character), but no deal breaker and if you feel strongly about it, keep it.
All in all, very cool! Move on to splines and put in the finishing touches!