Is twin brother of Aaron Ashmore.

For his made-for-television movie, Cadet Kelly (2002) (TV), he had to attend military school for 3 months, also taking voice lessons to be able to project as a cadet major.

Reunited with actor Eugene Lipinski (Del McAllister in Guitarman (1994) (TV)) after 4 years for the hit television series "Animorphs" (1998).

For X2 (2003), he had to undergo physical training for 6 months with no alcohol consumption and a strict diet.

When filming "Animorphs" (1998) he had to pet a tiger. During one scene, the tiger jerked its head and Shawn's fingers went up its nose. Luckily, the tiger's trainer helped him escape injury.

Has his grandfather's initials tattooed on his wrist, as does his twin brother Aaron.

His X-Men character, Bobby Drake/Iceman, was the first character from the comic series to make an appearance in another medium, as one of the main characters on Spider-Man and his Amazing Friends. His character, and Ray Park's character of Toad, have both appeared in animated adaptations of the comics. In both, their characters were voiced by Frank Welker.

Taught Aaron Stanford the lighter tricks he used in X2 (2003).

Landed a role as his brother's twin in the movie My Brother's Keeper (2004) due to come out in Spring 2004.

For the 2005 TV movie Terry (2005) (TV), Shawn's prosthetic leg was digitally added in. However, for long-distance shots, Grant Darby (a leg amputee and a world triathlon champion) was used as a double.

Stayed in contact with co-star Anna Paquin (Rogue) after filming X2 (2003).

Attended the 2004 MTV Movie awards with actress Michelle Trachtenberg.

Attended Turner Fenton High School in Brampton, Ontario.