Retime your video clips without making any cuts.
Forwards, backwards, freeze frame, oscillate, loop and stop motion… or any combination thereof. Gif-ify (if that’s a word), instant replay, emulate claymation, whatever you want to do.
This effect can be *told* how many frames are involved! No matter how long your clip is, there is a calculator built in to assist in designing your effect. (The dashboard calculator can be set to display percentages as well — or ignored altogether.)
Make room for extended animations/retimings by using the standard FCPX retiming mechanism and drag out a clip for the length of time required. Here’s an example, a 12 second 14 frame 24fps clip extended to 1 minute 25 seconds (and a few frames):
S•C Retimer can also be used to create easy cinemagraphs: