Poirot meets Miss Marple, Lord Caterham and his daughter, Bundle

Poirot met Miss Marple
in the little shop for tea.
‘Mon ami, Oh, I am distressed
at these recent movies on TV
supposedly of me!
They change my stories ’til I find
my little grey cells they so confuse.
I wonder why M. Suchet didn’t
these muddled tales refuse?’

‘Oh, Mr Poirot, yes I feel
puzzled when I see
Joan Hickson changed
to other people,
– all representing me!’
and, yes, some of these tales, I fear
are altered now so much,
and with many others that are shown,
I never was involved at all
(as is popularly known),
Oh, dear.’

‘Now, look who’s come, Lord Caterham,
with Bundle, too – sit here!
and tell us have they made a film
where both of you appear?’
‘Oh, we did enjoy that teasing man
John Gielgud acting me’,
said Caterham, with fervent verve,
‘and Cheryl Campbell had such fun
depicting Bundle’s rush and headstrong nerve
in that faithful, jolly adaptation*
of the sad old comical mystery
with secret societies, clocks and spies
– the kind of plot Mrs Christie could devise …

… may we join with you for tea?’
*Seven Dials Mystery (TV movie 1981)

[IP: four fictional characters from different works meeting. I don't know whether that was meant to be four different works, Poirot and Miss Marple were each separately in many books,of course; I think the other two just in two and together!]