Attach a Cat Avatar to your present avatar of any kind, by left clicking on the cat you wish to attach to your avatar, using interactive KittyCats Menu. You must be the owner of the KittyCat Click Interact Click Cat Avatar Click Continue A message box pops up saying it formed a folder called "KittyCats Avatar (right click & select "Replace Current Outfit") Find the Inventory folder in Recent, highlight the folder name and right click, and select Replace Current Outfit. The SL Viewer crashes instantly with no error messages. When you relog back in, your avatar is now the KittyCat, and your prior avatar is removed except for vital parts for any SL avatar needed to form the alpha system body. This is normal. It makes no difference whether you replace your outfit as a human, or other animal such as another cat. This occurs in the SL ExtraFPS release viewer, and also in the Firestorm ExtraFPS viewer, see FIRE-35022 I have had one occasion when using the KC designed procedure for attaching a Kittycat avatar, when using a human avatar to start the transfer on a new region, there was no crash. Subsequent trials all crashed. So you should repeat this more than once to confirm this bug. Note these crashes have never occurred before, with prior viewers, based on 12 years and over 2000 cat avatar transfers via Replace Current Outfit. This is a new bug for me. https://jira.firestormviewer.org/browse/FIRE-35022