Dreamworks has released a new $5 Megamind Blu-Ray or DVD printable coupon. Best Buy has the Megamind Blu-Ray Combo pack on sale for only $19.99 through 2/26. Use this coupon to get the Combo Pack for only $14.99! You can also get the DVD alone for only $8.99!
If you have the Best Buy ad, you could try to price match at Walmart or Target, but you may have some trouble because this price is only available today and tomorrow. It should work, but YMMV.