Questions 1, 2, and 3 were provided by the Cosmic Treadmill. They apply strictly to the Adventure Comics run and not any other series. Other than that, this was your quiz for March, which comes in like a Nitwonian Nibbybug and goes out like a Tulvanian Witch Wolf.
Too bad you guys are so smart, you got these answers pretty quickly.
1. Which Legionnaire was listed in the roll call with the wrong gender?
Bouncing Girl was in the roll call on the splash page of ADV 315.
2. Which two Legionnaires exchanged the first on-panel kiss during the Adventure Comics run?
Ironically, Element Lad and Light Lass, ADV 326.
Note that Light Lass could barely keep from LOLing.
3. Which Legionnaire(s) cross-dressed during the Adventure Comics run?
Chameleon Boy masqueraded as Cosmic Boy’s “date” in ADV 303, and Lightning Lass was disguised as her brother in ADV 308. Of course, it wasn't the fact that she looked, sounded, walked, talked, and smelled like a girl, it was the fact that she had no Adam's apple that gave her away. She would have gotten away with it, too, if not for those meddling kids!
4. What is the sound that Arm-Fall-Off Boy's arm makes when it comes off?
Not "Plop!", which might be expected, but "Plorp!".
5. Who was Quantum Queen's twin brother?
Via the Silver Age Legion Clubhouse:
Reader Dave Broomhead suggested the character Quantum Lad, who could project a laser beam, turn into a ray of light, pass through transparent objects, and dazzle foes (Bits of Legionnaire Business, ADV 337). Reader James Hankard asked Legion Editor Mort Weisinger if the Legionnaire on the cover of ADV 354 was Quantum Lad's girlfriend and Mort indicated that she was his twin sister (ADV 371 letter column).
6. During the Great Darkness Saga, Shadow Lass' costume was destroyed. What did she end up wearing?
She put on a Science Police uniform that was lying around. After that she found a new costume, which covered her from neck to toe in black.
7. Name three Legionnaires who gained additional powers after joining the Legion.
There have been lots of them. You guys came up with Kinetix, L2 Violet, L1 Lightning Lass, L2 Spark, L1 Karate Kid II, L1 Princess Projectra, Livewire, L1 Invisible Kids I and II, L1 Dream Girl, L1 Sun Boy, Apparition, Ferro, and probably more.