Slippery reads as follows: Trait. Attach this card to yourself. Duration 3 At the start of each round you Move 3, Free Move. This Move ignores Encumber effects. Currently, Slippery acts as follows: At the start of each round, the caster moves the target 3, Free Move. This Move ignores Encumber effects. Steps to reproduce: Cast Genetic Engineering on a different player's character (easiest in co-op). Get Slippery. Wait for upkeep.
erm, you'd have to do it for dimensional traveller as well. The bad part of this change is when GE is casted on the enemy (either by mistake or deliberate strategy), Slippery will let the enemy control their move. Ditto for Immovable and DT.