Tottoko Hamtarou OVA 1: Hamtaro no Otanjoubi - Mama wo Tasunete Sanzen Techi Techi
English name: Hamtaro: Hamtaro's Birthday! - 3000 Hammy Steps in Search of Mommy
Genres: Adventure, Comedy
Type: OVA, Episodes: 1
Aired: Nov 21, 2002
Studio: TMS Entertainment
Source: Unknown
Rating: G - All Ages
Synopsis:
Laura tells Hamtaro where he came from yet Laura thinks it is not true, just in time for his birthday, Hamtaro sets out with Boss and Oxnard to visit his mother to see if what Laura said is true, while the other Ham-Hams set up a surprise birthday party for him.

(Source: Wikipedia)