There are a LOT of events on 3/31.
In addition to those below, LaLaLu might appear at NHK on 3/31..

2002.03.31 Seiyuu Wave Bus Mystery Tour
  Mizuno Manabi
  Takahashi Mikako
  Kugimiya Rie
  Nasu Megumi
  Suzuki Chihiro
  Nakahara Mai
  Saitou Chiwa
  Asano Masumi
  Shimono Hiro

2002.03.31 Happy! Smile! Hello! signing session at Gamers
  Enomoto Atsuko

2002.03.31 Ouji-sama LV1 signing session at Animate Shibuya
  Chiba Susumu

2002.03.31 [18:30] Chou Bakuretsu Ranman Musume stage
  Miyanishi Noa
  Akimoto Noe
  Hayashi Akari

2002.03.31 [14:00] Tokyo Myuu Myuu anime event in Yamaha Hall
  Nakajima Saki
  Kakazu Yumi
  Asada Yoko
  Mochizuki Hisayo
  Noda Junko

2002.03.31 [14:30] Tenchi Muyou! GXP event in Ginza Gas Hall
  [don't know who the guests are yet]

2002.03.31 [14:30] Chobits TV anime talk and live in Kudan Kaikan
  Tanaka Rie
  Kumai Motoko

2002.03.31 [18:30] Chobits TV anime talk and live in Kudan Kaikan
  Tanaka Rie
  Kumai Motoko

2002.03.31 [15:00] Starchild Festival 2002 Spring
  Hayashibara Megumi
  Horie Yui
  Mizuki Nana
  Tokunaga Ai
  Kuwatani Natsuko
  Kobayashi Yumiko
  Nazuka Kaori
  Fukui Yukari
  Akita Madoka
  Asagi Mai
  Asakawa Yuu
  Matsuoka Yuki
  Saeki Tomo
  Higasayama Tsugumi

2002.03.31 Happy Lesson TV Zenyasai talk and live in Nihon Seinenkan
  Inoue Kikuko
  Asano Ruri
  Kimura Akiko
  Sasajima Kaoru
  Koyama Kimiko
  Shima Ryouka
  Sonozaki Mie
  Nakagawa Akiko

2002.03.31 Hayami Sho CD and Photo Collection signing session in Animate Kyoto
  Hayami Sho

2002.03.31 Nagoya TV Matsuri
  Matsumoto Rica

--
Hitoshi Doi                                               Toshi Nibunnoichi
http://www.win.ne.jp/~doi/                                    doi@win.ne.jp