I don't know what could be keeping Bruce Wayne, but we just can't hold this up any longer.

8 seconds sound clip from Batman (1966) - Batman Is Riled (S1E6) TV Series.

You can hear this line at 00:18:11 in the Blu-ray version of the movie.

Quote context

[...]

(Champagne pop)

(The Joker laughing)

- Here, Queenie, you know what to do with this now.

- Tomorrow night, champagne for everybody!

- What's this? Batman and Robin done in by a bottle of champagne? Impossible!

- I don't know what could be keeping Bruce Wayne, but we just can't hold this up any longer.

- Ladies and gentlemen, it gives me great pleasure to present the two people who will christen the S.S. Gotham.

- They hardly need an introduction. Batman and Robin the Boy Wonder.

- What are you two guys doing out here when The Joker is out there taking over the city?

- Uh, sorry about that, Batman.

[...]