Otis Sudeikis is growing up so fast!

Olivia Wilde — who is pregnant with Baby No. 2! — took to Instagram on Thursday, Sept. 1 to share a rare photograph of her two-year-old son, Otis.

Though one of the toddler's toy trucks is in the foreground of the picture, the 32-year-old actress' little boy — who looks so big! — can be seen playing in the background. "Not sure who loves the miniature toys more. (For size reference, this beauty can haul exactly four peanut M&Ms at a time. So I've heard)," Olivia captioned the cute pic.

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The Tron: Legacy star and her fiancé, Jason Sudeikis, 40, welcomed Otis in April 2014. The couple — who became engaged in January 2013 — previously announced they are expecting their second child together last April.

Click through the gallery below to see more of Hollywood’s cutest kids!