As it were, the main male character, Paul Giamatti, who plays a Super in the film, was repairing a garbage disposal. He instructed the slackers not to put anymore clothing down the disposal. He also had the rule that there was to be no smoking indoors. As Giamatti’s character, Cleveland Heap, exited the slackers’ apartment, he yelled at them to stop smoking indoors. As he did, the next line of dialog spoken by the John Lennon-esque member of the slacker group was, "Baby's on the Half-Tip!" And there was much rejoicing among the slackers.
2. As spoke when something good, exciting or wonderous has occured. Akin to being "off the chain".
Example, "Gina got over her car and threw a big party to raise money for a new paint job. You should have seen that place. Baby's on the half-tip over there!