1. "I am afraid that I cannot be christened at present, as my parents are both dead." (Jack)
This is a classic example of Wilde's wordplay, with "christened" alluding to both religious baptism and the act of giving a name. Jack's statement implies he's unable to change his name because his parents are dead, but it's a sly joke because he's already changed his name to Ernest.
2. "I don't know that I am particularly anxious to be christened, I must say. It is a painful and tedious business, I believe." (Jack)
This is a witty double meaning, as Jack is referencing both the literal act of baptism and the idea of changing his identity, which he finds uncomfortable.
3. "I don't like the look of that fellow. I am quite sure he is a Bunburyist. I know the type." (Lady Bracknell)
This is another example of Wilde's clever use of language. Lady Bracknell is using "Bunburyist" to refer to someone who uses an imaginary invalid to avoid social obligations, but she also uses the word to imply that Jack is a "bad character" or a "liar".
4. "I'm glad to hear it, as I have been meaning to ask you for some time to christen some soup for me." (Cecily)
Cecily is making a joke about the name "Ernest," as it sounds very similar to the word "earnest," which means sincere or serious. This reinforces the theme of names and identity in the play.
5. "I'm not going to be lectured by you, Jack. I was only a girl, and you were only a boy. We were both very young and very foolish." (Gwendolen)
This is a pun on the word "boy," which can refer to a young man, but also to a young dog. It's a humorous way for Gwendolen to dismiss the idea of a romantic relationship between Jack and Cecily.
These are just a few of the many puns in Act 3 of "The Importance of Being Earnest." Wilde's use of wordplay is crucial to the play's comedic effect and its exploration of themes like identity, social expectations, and the absurdity of Victorian society.