I didn't get this. Is it a flashback he's remembering, or is Pintsize making up a story?
I'm a bit torn between two options:
1) Panels 2,3 and 4 Pintsize is telling a story, panel 4 is obviously typical Pintsize
2) Panels 2 and 3 Marten is telling about how he came to the office, and then Pintsize interrupts and keeps on telling the story, as told in panel 4, totally making Marten mad, and Momo scandalized.
Either way, the beginning of the story is somewhat believable, and panel 4 is just a joke by Pintsize.
I saw earlier in the thread that someone told about "shirt discontinuity"
I would not be surprised that Jeph's initial intention would have been to use the discontinuity as a clue that the infringin panel was a spin off the initial thread, indicating that panels 2 and 3 were Marten's and panel 4 Pintsize's. But I haven't seen such discontinuity, since it is also claimed in the thread that such discontinuity has been "fixed".