not the kidnapping subplot. which i mentioned was bad. lloyd interferes with it, because he grabs the samsonite bag and he ends up keeping it and brings it back home after he gets fired. later they discover their bird has his head wrenched off and they wanna leave and head for aspen. lloyd tapes the bird's head back on and sells it to a blind kid in the apartment complex. that is the funny. the image of the blind kid saying pretty birdy by itself isnt funny if you didnt have the setup line from LLoyd, "i took care of it". that is called The payoff, popularized by family guy.
if all you have is a kid in a wheelchair saying "pretty birdie" i wouldnt be laughing.