“Forget” vs. “would forget” vs. “forgets”

Question

Is the format of this sentence correct:

If he had to describe himself in 5 words, he’d say he’s curious. And then forget to give you 4 more words.

There were some conflicts between a colleague and me, whether or not the sentence should be one of the following:

• If he had to describe himself in 5 words, he’d say he’s curious. And would then forget to give you 4 more words.
• If he had to describe himself in 5 words, he’d say he’s curious. And then forgets to give you 4 more words.

Answer 1

The first thing to say is that you might want to change ‘he’d say he’s curious’ to ‘he’d say he was curious’, because it’s reported speech.

‘And then forget’ is an ellipsed form of ‘And then he would forget . . .’ and there’s nothing grammatically wrong with it (‘then’ can come before or after ‘would’).

In the example

If he had to describe himself in 5 words, he’d say he’s curious. And then forgets to give you 4 more words.

the tenses are out of sequence. For it to work, you’d have to change the verb forms in the first sentence and say

If he has to describe himself in 5 words, he says he’s curious. And then forgets to give you 4 more words.

Answer 2

The most common correct way would be:

If he had to describe himself in five words, he'd say he's curious. And then forget to give you four more words.

There is an implicit "would" before "forget" in the second sentence, but it is usually dropped using ellipsis. This is why it's not "forgets". Putting the "would" in is still correct, but sounds overly formal to me.

Answer 3

If he had to describe himself in 5 words, he’d say he’s curious, forgetting to give you 4 more words.

Or

If he had to describe himself in 5 words, he’d say he’s curious. And would then forget to give you 4 more words.

The second being less formally correct but still not wrong to my ear, because the full stop followed by "and" suggests a continuation which, when written formally should be more explicit.

While making sense,

If he had to describe himself in 5 words, he’d say he’s curious. And then forgets to give you 4 more words.

is even less correct as this compounds the error with an incorrect tense of "forget"

Answer 4

To be strictly grammatically correct, you should say, "If he had to describe himself in 5 words, he would say he’s curious. He would then forget to give you 4 more words." Your original second sentence has no subject. But, especially in speech and informat writing, it's not uncommon to leave out the subject when it's the same as in the preceding sentence, especially if you want to indicate a rapid or abrupt sequence of events. "Bob heard the question. Answered it. Left the room."

You shouldn't say "he'd say ... and then forgets" because "he'd" is a contraction of "he would", so you're switching from future conditional, "would say", to basic present tense, "forgets". The technically correct construct would be to match the tenses of the verb, "would say ... would forget". You can get away with dropping the second "would" as you're alrady dropping the second subject, but you shouldn't change endings or add words to explicitly shift the tense, like saying "will forget" or "forgot" or "forgets".

Well, you could always shift the whole thing to another tense, for example past: "When he had to describe himself in 5 words, he said he was curious. He then forgot to give 4 more words." Etc.