I'm pretty sure this is already known, but starting a recall on a skarner pillar just before it activates overwrites your recall animation with the pillar animation, effectively making your recall invisible. After the pillar animation has played your champion just idly stands there until they are recalled.
-stand on a pillar before it activates
-start your recall
-enjoy the magic
Yeah it's not game-breaking and will rarely if ever cause problems, but it might still allow for some stupid situations where someone recalls and the enemy team can't tell. Tested on Bard, but the nature of the bug leads me to assume it is champion-unspecific.