Oh, I checked all my books, but I'm afraid... Well, it's like this...
6 seconds sound clip from Darkwing Duck - Dead Duck (S1E47).
You can hear this line at 00:19:43.098 in the DVD version of the TV Series.
Quote context
[...]
- There's nothing... There's nothing in this world as precious as life.
- If you only worry about yourself, you're just gonna end up lonely and unhappy.
- I am?
- Ye have to treat others with the respect and kindness that they deserve.
- Hey, what happened to respect and kindness?
- Hurry, Launchpad, we have to get to Morgana's before my hour's up.
- Oh, I checked all my books, but I'm afraid... Well, it's like this...
- The common cold goes away in three to five days. Death is a little more permanent.
- I'm very sorry, Dark, dearest.
- Mr. Mallard, I trust there won't be anymore stalling.
- Just give me one more minute to say goodbye.
[...]