Possible Clues:

• Like the blue whale, out of all animals
• Like Jupiter, out of all the planets
• Most immense
• Most magnanimous popular gestures, at heart
• There's nothing bigger in case containing plastic rag
• Like Ganymede among Jupiter's moons
• Most great least great, only 40% off
• Like the outer matryoshka doll
• Most enormous rat's leg, broken
• Superlatively extensive and somewhat popular gesture