你根本不应该使用time.sleep，因为它不适合asyncio，而discord.py是基于asyncio构建的。相反，我们应该有一个配对列表，随机选择一个，然后使用asyncio.sleep在消息之间暂停。

jokes = [
    ('Can a kangaroo jump higher than a house?', 'Of course, a house doesn’t jump at all.'),
    ('Anton, do you think I’m a bad mother?', 'My name is Paul.'),
    ('Why can\'t cats work with a computer?', 'Because they get too distracted chasing the mouse around, haha!'),
    ('My dog used to chase people on a bike a lot.', 'It got so bad, finally I had to take his bike away.'),
    ('What do Italian ghosts have for dinner?', 'Spook-hetti!')]

setup, punchline = random.choice(jokes)
await client.send_message(message.channel, setup)
await asyncio.sleep(3)
await client.send_message(message.channel, punchline)

你的做法全错了。

a = 'Can a kangaroo jump higher than a house?' + time.sleep(3) + 'Of course, a house doesn’t jump at all.'

将不工作，原因是因为你想time.sleep(3)是一个字符串，对于每一个这些你会从（据我所知）.需要做以下

await bot.say("Can a kangaroo jump higher than a house?")
time.sleep(3)
await bot.say('Of course, a house doesn’t jump at all.' )

当然，您需要将bot更改为客户端，但这基本上是您必须做的。
不起作用的原因：执行a = "string" +func()+"string2 ; print(a)"会给予错误，因为您将其视为字符串。