Hijack

Hijack is an option in Completing the Mission during the "Toppat 4 Life" pathway.

When chosen, Henry Stickmin enters the Big Boy and attempts to destroy the base, but the tank's mechanical anomalies caused it to reverse instead, killing Madd Ladd and sending the vehicle down the cliff, resulting in a fail.

Fail Message
AND you forgot to signal. Sheesh!

Trivia

 * Since the Big Boy has extremely thick armor and the elevation isn't too high compared to its size, the tank and Henry likely survived the fall.