The scene where John is dealing with the dog who has OCD. He's trying to get him to not obsess over throwing the ball, but it's not working so Lucky and Rodney cry out. "Throw the damn Ball!" and Rodney delivers a great comeback, "You can't save 'em all, Hasselhoff!"
The fact that the OCD dog is voiced by Gilbert Gottfried.
When John pretends he's bought Lisa a fancy new sports car. And teases her about it.
Lisa: Oh, my God! John, you didn't!
John: No, I didn't. The van's around the corner. But don't tell me you don't care about money.
Lisa: That's not funny.
John: (starts imitating her)Oh John, you didn't! You didn't!
Lisa: (starts laughing under her breath) That's not funny.
When poor Maya asks her dad to find her missing pet guinea pig. And her dad doesn't comfort her at all.
Dr. Dolittle: I'll put down some of that sticky paper for him.
Maya: No, not the sticky paper!
Dr. Dolittle: It'll be fine. You peel him right off it, he'll live.
This is followed up by a sequence in which Dolittle is laying alone in bed (the family off at camp), and on top of him is a veritable landmine of just about every type of mouse or rat trap you could possibly think of. Rodney successfully navigates through all of them without setting them off, ending up squeaking right in front of his face, waking him up and causing him to scream like crazy, leading into the next sequence...
The whole Dolittle/Rodney scene. Which eventually ends with Rodney's cage is strapped to the top of Dolittle's car, which happens to be cruising down the highway!
Rodney: Come on, Doc! I'm getting whisker-whipped up here! Dr. Dolittle: One more word, and I'm letting you out! I'll leave you in the wild! With the REAL animals! See how much talk you do when squirrels are kickin' in your ass! Rodney: Fine, then! I'll just sing! (he then proceeds to sing "Blowin' In the Wind," way off tune) The answer, my friend, is blowin' in the wind. Dr. Dolittle: SHUT UP! (turns the radio on to full blast) Rodney: (still singing) This guinea pig is blowin' in the wind! Dr. Dolittle: I can't hear you! I'm groovin'! Rodney: Why do they call me "guinea pig," anyway? I ain't Italian, and I'm not pork! Dr. Dolittle: SHUT UP, I SAID!
Then, later, Dr. Dolittle arrives at the camp and Rodney is up on the roof. He asks his Dad if they still have those B.B. guns he used to play with when he was a kid, and Rodney shouts "Crazy man! Lunatic! Psycho!"
The scene where John and the two rats are in a hospital room, and he's performing a diagnosis on one of the rats due to it feeling supposedly ill...only for his wife Lisa and co-workers to enter the room and ask him what on earth is he doing, and for him to start arguing with them. Ridiculous enough, but then the rat supposedly goes into cardiac arrest, upon which John, then starts performing on the rat mouth-to-mouth CPR, with his wife, coworkers, and the other rat being absolutely aghast. What really sells the scene is how the scene is framed in an entirely serious manner through both the dramatic music as well as John and the other rat's panicking reactions frame the scene in an entirely serious manner, which just makes the absurd situation all the more uproarious. And then to top it all off, the unconscious rat recovers with a series of farts.
John: (to wife and coworkers) He just had gas! (Lisa only gives him a concerned Blank Stare)Lisa, stop looking at me like that. (Naturally enough, the very next scene is Lisa admitting John to the Hammersmith Retreat lunatic asylum.)
John's breakdown at the lunatic asylum. This happens after Lucky visits him to talk about Jacob's (the tiger) worsening suicidal condition, but Dolittle brushes him off because, according to him, Lucky (as well as other animals that have been talking to him) caused him to be placed in an asylum in the first place. (It does make a whole lot of sense, in a disturbing way, when you alternately view this as a psychological thriller disguised as a PG-13 family comedy.)
John: (after Lucky leaves, he yells at the sky) That's to all of y'all! Leave me alone! Stop talking to me! (proceeds to scream like an actual lunatic, then departs into the asylum... and screams at the patients looking at him, scaring them in the process)
Of course, the very next scene shows Dolittle coming into the office of the head doctor of the asylum, now completely calm and sane again, requesting to be released, believing he's now completely cured of his lunacy, though he has to bribe and threaten the doctor with revealing the doctor's dirty little secret to convince him to sign the release forms.
Lucky's suggestion for a name: "One girl called me: 'Please Mommy, not him'."
When the good doctor is talking to Lucky for the first time, we get this:
Dolittle: Stop it! You can't talk! Dogs don't talk!
Lucky: What the hell do you think barking is? An involuntary spasm?
Dr. Dolittle has just heard Rodney talking for the first time and is about to abandon him on the side of the road when he's approached by a couple of local yokels.
Woman: Need some help?
Dr. Dolittle: Oh, no, I'm - we're - we're fine. I'm just stretching my legs a little here.
Rodney: Ask her if she's got any lettuce!
Dr. Dolittle: Shut your mouth. Shut your furry little mouth right now!