Not sure how to incorporate this fact into our articles, but apparently according to the book — just as Bob, Emily and Tim were played by Kermit, Piggy and Robin — the characters of Peter, Betina and Belinda were actually played by Simon, Miranda and Melinda.
Which book we talkin'? I assume not this book which uses actual photos from what I can see on eBay. If we have whatever edition this is on the Wiki, we note it on that page, and note it on the character pages with a link to said book page.
But Betina and Belinda already has that recording studio pic, so a crop of the Through the Window back cover could go there, maybe even a Behind the Scenes/Off Set sort of note. The Peter Cratchit page currently cites Rizzo saying in Blu-Ray audio commentary that "Peter Frog" played the role, so it could go in that same section, treated in the same way.