I vote for the one where she’s an outdated soviet giant fucking tank secretary with a tinny, robotic but recognisably russian accent and has a remote link to a satellite missiles platform that comes into play as Beck’s super move.
Collect enough rare diesel canisters (ancient and obsolete fuel-type, hard to come across) and she will drop into a level to allow Beck to hop onto her giant-ass shoulder where you’ll control her Metal Slug style. You’ll be able to just straight run everything over, giant exhaust pipes rumbling whilst multiple turrets on her massive chassis belch shells and bullets unreservedly across the screen. Infinite ammo, short duration. She’ll have ghetto-ass, brutal versions of all of Beck’s so far learned abilities, like rockets for super jumps, giant drills for digging, super-speed tank tracks for dashes etc.
Things will get fucked harshly until Call runs out of diesel, at which point she will shrug you off and rocket herself out of there.