My ventilation ducts will be too small to crawl though.
Fortunately, most real-life ducts are already like this, but certainly we see in drama that hero-sized vents are the norm in most places.
This advice can be equally helpful for other things that might be similar to a ventilation duct, like garbage chutes, to prevent getaways for those pesky heroes whom your legions can never hit despite all being trained in marksmanship.
Plot armor is a real bitch sometimes.
If you're an evil overlord stuck in a comedy film, things are sure to go badly for you. Do your best to jump to a drama, where you might win, if it's like a Greek tragedy or something. Take cues from these all-time losses in comedies.
Spaceballs - Lord Helmet had a Schwartz duel with Lone Star near the ship's self-destruct button, and ended up pressing it when he was defeated (there are actually 2 other mistakes in here Lord Helmet should have avoided, had he consulted the Evil Overlord List™, but we'll save those for another day).
The Incredibles - After Edna talks about how foolish capes are, Syndrome gets his own cape caught in his own jet's turbine, causing him to be sucked in, himself destroyed, and his plane exploding. Syndrome also failed to consult the list when he tried to take over the world, which caused him to make innumerable mistakes that led to his defeat.
Drama or bust if you happen to be an evil overlord in a fiction of some kind. Learn from our predecessors' examples, fellow overlords!
How to tell you're in a comedy: the duct collapses and the hero falls from the ceiling in front of you.