Random high jump like a footstool, but isn't.

[Melonfrog]

Has anyone ever randomly flew high into the air as if you footstooled, but you know you didn't?
This is hard to explain so I will try by example.

1v1 for Glory Charizard vs Wario

Charizard launched Wario off stage and attempted to gimp, he misses so used his remaining jumps to get back on stage. Wario is also jumping back onto the stage in a panic.
Wario grabs the ledge meanwhile Charizard is just behind him with his last jump ready to be used.
Charizard suddenly jumps really high, Charizard looks confused and then uses Fly into his confusion landing straight into a F smash from Wario.

This is from my recent replay against a friend, he said it sometimes happens to him but has no idea how to do it purposely.
What is it and how did I do it? Have you ever done it?

 

[GSM_Dren]

This occurs because the footstool does happen, but there is no animation because the player being footstool'd is already in an active state (grabbing the ledge, in the middle of an up-b, etc.) If I recall correctly, the whole footstool animation happens when the other player is not doing anything or gets footstooled in the middle of their jump.

 

[Melonfrog]

That makes sense. I though it was a glitch or something.

 

[Kwam$tack$]

yeah it happens pretty often. really annoying. i figured it was a lag thing like when u press the c-stick in the air during lag and a nair comes out instead of the direction you pressed