The TAS by mikeSpeedyAdventures contains dozens and dozens of small optimizations (particularly regarding movement). Shout-outs to Mike for that one! It's a great resource to learn all those details that can help you improve your times dramatically.

Here are a few more of those small optimizations. Let's start with the ones I'm reasonably certain about.

• Switching to Hoagie and back to Bernard after opening the grating means you don't have to wait for the screen to scroll before the salesman starts talking. Not sure whether it saves time for the TAS, but for humans it saves about 0.5 seconds.
• At Green's, once you've pushed the speaker, using the stereo (make sure it's the stereo and not the on/off button) before picking up the videotape is about 0.2-0.4 seconds faster than picking up the videotape first.
• When entering Washington's room with Hoagie, it's possible to save at least one frame over the TAS by correctly timing your clicks on the bed, as shown in the Washington's bed video.
• In the attic, immediately going to the roof seems 0.3 seconds faster than using the mattress first.
• After picking up the quill pen, it's possible to start walking diagonally to the left. Saves one or two frames.
• With Bernard, schmoovement on your way to pick up the crank (after using the rope with the pulley) is about 0.2-0.3 seconds faster.
• When you're back outside after pulling the rope the first time, you can use schmoovement on your way to the mansion's door. Saves about 0.3-0.4 seconds (one or two frames faster than the TAS).
• With Laverne, it's possible to use the crank with the crank box one frame earlier than what the TAS does. The using the crank video shows where and when to click.
• With Laverne, every time you come back from the main hall, wait a little bit before clicking anywhere. Saves about 0.1-0.2 seconds over the TAS. Check the opening the clock with Laverne video for an example.
• Finally a significant one. To pick up the vinegar, first click below the table leg and then use the can-opener with the time capsule. Saves about 0.6-0.8 seconds.
• After getting the vinegar, on the way to the mummy's room, clicking below the weird column in the middle before clicking on the mummy's room's door is about 0.4 seconds faster.
• After getting the cat, you can use schmoovement on the way to the mansion's door. Saves about 0.1-0.2 seconds.
• Using the hamster with the microwave and stopping is faster than walking all the way to the microwave, as mentioned in the glitch explanations guide. This also means that using the microwave before going to the laundry room is about 0.2 seconds faster than going to the laundry room first.
• After using the vacuum cleaner and picking up the hamster one last time, switching to Hoagie or Bernard and back to Laverne means you don't have to wait for the screen to scroll before using the hamster wih the generator. Saves between 0.5 and 1.0 seconds.
• At the very end of the game (after using the bowling ball with the Purple Tentacles), schmoovement on your way to talk to the Purple Tentacle saves about 0.1 seconds.

And here are a few I'm not so sure about.

• Instead of picking up the dime at the beginning, I pick it up when coming back downstairs after getting the keys and the gun. This makes inventory management not-unreasonably-hard, and it seems to be 0.2-0.3 seconds faster than picking it up after getting the flier. But I didn't compare it against picking it up at the beginning.
• With Hoagie, schmoovement on the way to the mailbox (when Hoagie is above the carriage, walking diagonally, and his sprite is sideways) saves about 0.2 seconds or so.
• It's possible to pick up the teeth from a slightly different position just as they're entering the grating. When that happens, the animation of Bernard picking them up is about 0.5 seconds faster. I've only managed to do it once, though (during a practice session). Check the fast teeth video to see it in action.
• Schmoovement on your way to pick up the blanket (after talking to Washington) might save a frame.
• Schmoovement on your way to pick up the oil (after filling up the bucket) might save a frame.
• Picking up the lab coat after finishing the battery doesn't seem to be slower than picking it up after your first conversation with Red, and it makes inventory management a bit easier.
• When optimized, switching hammers on your way upstairs seems just as fast as switching them on your way back downstairs.
• I made a note that says that, when leaving the mansion with Hoagie, assuming you're coming from the main hall, clicking on the left of the mansion's door first and then clicking on the door is a frame faster if you time the second click right. Don't have video proof, though.

Here are some things that the TAS does but you might not notice that they're faster than the alternatives.

• While Hoagie is opening the door to the main hall, hold Enter to enter the main hall instead of spam-clicking. That way the door will remain open.
• In Dwayne's room, looking at the TV set is faster than using the TV set.
• After using the rope with Dr. Fred, pulling the rope is 0.2-0.3 seconds faster than pulling the pulley.
• In the future, picking up the sweater is faster than directly using the hamster with the sweater.

And, finally, a couple of curiosities that as far as I know are completely useless.

After using the blanket with the chimney, you can go outside and give the wine to Jefferson there. You can also paint the tree at this point (Hoagie will distract them). However, it loses time because here you can't talk to Washington in order to make him cut down the tree.

In the future, you can pick up the flag, go back to the kennel, and ask for a toilet break. Then you can go to the area with the Chron-O-John and use the flag there. Now, if you pick up the cat and go back to the kennel, the guard will be already there somehow. Useless, but now there's an extra line of dialogue, and after that you have one frame where you can do an action before the guard says the "SAY, cutie!" line. You can use that frame to use the cat. And... it's useless. The guard doesn't let you use it and then proceeds to say the "SAY, cutie!" line as usual.