Introduction:
The play 'If I were you' by Alan Ayckbourn is indeed humorous. The playwright masterfully uses witty dialogues, situational irony, and comedic timing to create a light-hearted and entertaining atmosphere throughout the play. The audience is constantly engaged and amused by the amusing incidents and funny interactions between the characters.

Instances of Humor:
1. Dialogue humor: The play is filled with humorous dialogues that add to the comedic effect. For example, in Act 1, when Malcolm discovers that Henry has swapped bodies with him, he exclaims, "I mean, what would I want with a body like that? That's not me, that's not Malcolm!" This line not only highlights the absurdity of the situation but also elicits laughter from the audience.

2. Situational irony: The play revolves around the concept of body swapping, which in itself is a humorous and absurd situation. The characters find themselves in hilarious scenarios, trying to navigate each other's lives. For instance, when Henry, in Malcolm's body, tries to act like Malcolm, he struggles to adapt to Malcolm's mannerisms and ends up comically failing in his attempts.

3. Physical comedy: The play also incorporates physical comedy to enhance its humor. In Act 2, when Malcolm, in Henry's body, tries to imitate Henry's walk, his exaggerated movements and awkward posture create a comical visual effect. The audience cannot help but laugh at his clumsy attempts at mimicking Henry's distinctive gait.

4. Comic timing: The timing of the humorous incidents and punchlines is impeccable, contributing to the overall hilarity of the play. For example, in Act 3, when Henry, in Malcolm's body, accidentally knocks over a vase, the timing of the sound effect and the characters' reactions create a comedic moment that leaves the audience in splits.

5. Wordplay: The play also incorporates wordplay to create humor. In Act 1, when Malcolm, in Henry's body, is trying to convince Henry's wife that he is Henry, he says, "Look at me! I'm Henry! If you don't believe me, ask Henry!" This clever use of words and irony adds to the comedic effect and generates laughter.

Conclusion:
The play 'If I were you' is undeniably humorous, with its witty dialogues, situational irony, physical comedy, comic timing, and wordplay. The playwright skillfully uses these elements to create a light-hearted and entertaining atmosphere that keeps the audience engaged and amused throughout the play. The comedic moments and funny instances in the play make it an enjoyable and delightful experience for the viewers.