Shorecrasher Mimic 
Creature — Shapeshifter
Whenever you cast a spell that's both green and blue, this creature has base power and toughness 5/3 until end of turn and gains trample until end of turn.
Legality
standardNOT LEGALpioneerNOT LEGALmodernLEGALlegacyLEGALvintageLEGALcommanderLEGAL