oldtisme

I have been asked to make Peppa Pig and her brother George costumes for Halloween. I'm planning on making them out of heaviest flannel I can buy so it will stay stiff as in the picture I'm hoping to attach to this. My question in what would be the best Interfacing or Fusible web to make them even stiffer to keep the shapes. These will be for my youngest grandson & granddaughter. I'd like to get them planned out & sewn the sooner the better (time to adjust any mistakes) But as I stated what would be best to make them stiff to hold the shapes of the costumes. Thank you for all your informative answers to my question....as always I know who to go to for the correct solutions to my problems. Thanks to all the Quilt Board members, Yall are the greatest in my book!
OK now to attempt the best picture of them that I have found unless you want to Google Peppa Pig.
Well that was a big fail on posting a picture, but even if you don't Google Peppa Pig just let me know what you would use to make the heavy flannel stiff to keep it's shape. Thanks a BUNCH
Jeri